02_MySQL_DQL基本语法

相关代码GitHub仓库

git@github.com:tomxwd/MySQL-Basic.git

https://github.com/tomxwd/MySQL-Basic.git

这里是DQL（Data Query Language）

准备工作

建表；

/*
SQLyog Ultimate v10.00 Beta1
MySQL - 5.5.15 : Database - myemployees
*********************************************************************
*/


/*!40101 SET NAMES utf8 */;

/*!40101 SET SQL_MODE=''*/;

/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`myemployees` /*!40100 DEFAULT CHARACTER SET gb2312 */;

USE `myemployees`;

/*Table structure for table `departments` */

DROP TABLE IF EXISTS `departments`;

CREATE TABLE `departments` (
  `department_id` int(4) NOT NULL AUTO_INCREMENT,
  `department_name` varchar(3) DEFAULT NULL,
  `manager_id` int(6) DEFAULT NULL,
  `location_id` int(4) DEFAULT NULL,
  PRIMARY KEY (`department_id`),
  KEY `loc_id_fk` (`location_id`),
  CONSTRAINT `loc_id_fk` FOREIGN KEY (`location_id`) REFERENCES `locations` (`location_id`)
) ENGINE=InnoDB AUTO_INCREMENT=271 DEFAULT CHARSET=gb2312;

/*Data for the table `departments` */

insert  into `departments`(`department_id`,`department_name`,`manager_id`,`location_id`) values (10,'Adm',200,1700),(20,'Mar',201,1800),(30,'Pur',114,1700),(40,'Hum',203,2400),(50,'Shi',121,1500),(60,'IT',103,1400),(70,'Pub',204,2700),(80,'Sal',145,2500),(90,'Exe',100,1700),(100,'Fin',108,1700),(110,'Acc',205,1700),(120,'Tre',NULL,1700),(130,'Cor',NULL,1700),(140,'Con',NULL,1700),(150,'Sha',NULL,1700),(160,'Ben',NULL,1700),(170,'Man',NULL,1700),(180,'Con',NULL,1700),(190,'Con',NULL,1700),(200,'Ope',NULL,1700),(210,'IT ',NULL,1700),(220,'NOC',NULL,1700),(230,'IT ',NULL,1700),(240,'Gov',NULL,1700),(250,'Ret',NULL,1700),(260,'Rec',NULL,1700),(270,'Pay',NULL,1700);

/*Table structure for table `employees` */

DROP TABLE IF EXISTS `employees`;

CREATE TABLE `employees` (
  `employee_id` int(6) NOT NULL AUTO_INCREMENT,
  `first_name` varchar(20) DEFAULT NULL,
  `last_name` varchar(25) DEFAULT NULL,
  `email` varchar(25) DEFAULT NULL,
  `phone_number` varchar(20) DEFAULT NULL,
  `job_id` varchar(10) DEFAULT NULL,
  `salary` double(10,2) DEFAULT NULL,
  `commission_pct` double(4,2) DEFAULT NULL,
  `manager_id` int(6) DEFAULT NULL,
  `department_id` int(4) DEFAULT NULL,
  `hiredate` datetime DEFAULT NULL,
  PRIMARY KEY (`employee_id`),
  KEY `dept_id_fk` (`department_id`),
  KEY `job_id_fk` (`job_id`),
  CONSTRAINT `dept_id_fk` FOREIGN KEY (`department_id`) REFERENCES `departments` (`department_id`),
  CONSTRAINT `job_id_fk` FOREIGN KEY (`job_id`) REFERENCES `jobs` (`job_id`)
) ENGINE=InnoDB AUTO_INCREMENT=207 DEFAULT CHARSET=gb2312;

/*Data for the table `employees` */

insert  into `employees`(`employee_id`,`first_name`,`last_name`,`email`,`phone_number`,`job_id`,`salary`,`commission_pct`,`manager_id`,`department_id`,`hiredate`) values (100,'Steven','K_ing','SKING','515.123.4567','AD_PRES',24000.00,NULL,NULL,90,'1992-04-03 00:00:00'),(101,'Neena','Kochhar','NKOCHHAR','515.123.4568','AD_VP',17000.00,NULL,100,90,'1992-04-03 00:00:00'),(102,'Lex','De Haan','LDEHAAN','515.123.4569','AD_VP',17000.00,NULL,100,90,'1992-04-03 00:00:00'),(103,'Alexander','Hunold','AHUNOLD','590.423.4567','IT_PROG',9000.00,NULL,102,60,'1992-04-03 00:00:00'),(104,'Bruce','Ernst','BERNST','590.423.4568','IT_PROG',6000.00,NULL,103,60,'1992-04-03 00:00:00'),(105,'David','Austin','DAUSTIN','590.423.4569','IT_PROG',4800.00,NULL,103,60,'1998-03-03 00:00:00'),(106,'Valli','Pataballa','VPATABAL','590.423.4560','IT_PROG',4800.00,NULL,103,60,'1998-03-03 00:00:00'),(107,'Diana','Lorentz','DLORENTZ','590.423.5567','IT_PROG',4200.00,NULL,103,60,'1998-03-03 00:00:00'),(108,'Nancy','Greenberg','NGREENBE','515.124.4569','FI_MGR',12000.00,NULL,101,100,'1998-03-03 00:00:00'),(109,'Daniel','Faviet','DFAVIET','515.124.4169','FI_ACCOUNT',9000.00,NULL,108,100,'1998-03-03 00:00:00'),(110,'John','Chen','JCHEN','515.124.4269','FI_ACCOUNT',8200.00,NULL,108,100,'2000-09-09 00:00:00'),(111,'Ismael','Sciarra','ISCIARRA','515.124.4369','FI_ACCOUNT',7700.00,NULL,108,100,'2000-09-09 00:00:00'),(112,'Jose Manuel','Urman','JMURMAN','515.124.4469','FI_ACCOUNT',7800.00,NULL,108,100,'2000-09-09 00:00:00'),(113,'Luis','Popp','LPOPP','515.124.4567','FI_ACCOUNT',6900.00,NULL,108,100,'2000-09-09 00:00:00'),(114,'Den','Raphaely','DRAPHEAL','515.127.4561','PU_MAN',11000.00,NULL,100,30,'2000-09-09 00:00:00'),(115,'Alexander','Khoo','AKHOO','515.127.4562','PU_CLERK',3100.00,NULL,114,30,'2000-09-09 00:00:00'),(116,'Shelli','Baida','SBAIDA','515.127.4563','PU_CLERK',2900.00,NULL,114,30,'2000-09-09 00:00:00'),(117,'Sigal','Tobias','STOBIAS','515.127.4564','PU_CLERK',2800.00,NULL,114,30,'2000-09-09 00:00:00'),(118,'Guy','Himuro','GHIMURO','515.127.4565','PU_CLERK',2600.00,NULL,114,30,'2000-09-09 00:00:00'),(119,'Karen','Colmenares','KCOLMENA','515.127.4566','PU_CLERK',2500.00,NULL,114,30,'2000-09-09 00:00:00'),(120,'Matthew','Weiss','MWEISS','650.123.1234','ST_MAN',8000.00,NULL,100,50,'2004-02-06 00:00:00'),(121,'Adam','Fripp','AFRIPP','650.123.2234','ST_MAN',8200.00,NULL,100,50,'2004-02-06 00:00:00'),(122,'Payam','Kaufling','PKAUFLIN','650.123.3234','ST_MAN',7900.00,NULL,100,50,'2004-02-06 00:00:00'),(123,'Shanta','Vollman','SVOLLMAN','650.123.4234','ST_MAN',6500.00,NULL,100,50,'2004-02-06 00:00:00'),(124,'Kevin','Mourgos','KMOURGOS','650.123.5234','ST_MAN',5800.00,NULL,100,50,'2004-02-06 00:00:00'),(125,'Julia','Nayer','JNAYER','650.124.1214','ST_CLERK',3200.00,NULL,120,50,'2004-02-06 00:00:00'),(126,'Irene','Mikkilineni','IMIKKILI','650.124.1224','ST_CLERK',2700.00,NULL,120,50,'2004-02-06 00:00:00'),(127,'James','Landry','JLANDRY','650.124.1334','ST_CLERK',2400.00,NULL,120,50,'2004-02-06 00:00:00'),(128,'Steven','Markle','SMARKLE','650.124.1434','ST_CLERK',2200.00,NULL,120,50,'2004-02-06 00:00:00'),(129,'Laura','Bissot','LBISSOT','650.124.5234','ST_CLERK',3300.00,NULL,121,50,'2004-02-06 00:00:00'),(130,'Mozhe','Atkinson','MATKINSO','650.124.6234','ST_CLERK',2800.00,NULL,121,50,'2004-02-06 00:00:00'),(131,'James','Marlow','JAMRLOW','650.124.7234','ST_CLERK',2500.00,NULL,121,50,'2004-02-06 00:00:00'),(132,'TJ','Olson','TJOLSON','650.124.8234','ST_CLERK',2100.00,NULL,121,50,'2004-02-06 00:00:00'),(133,'Jason','Mallin','JMALLIN','650.127.1934','ST_CLERK',3300.00,NULL,122,50,'2004-02-06 00:00:00'),(134,'Michael','Rogers','MROGERS','650.127.1834','ST_CLERK',2900.00,NULL,122,50,'2002-12-23 00:00:00'),(135,'Ki','Gee','KGEE','650.127.1734','ST_CLERK',2400.00,NULL,122,50,'2002-12-23 00:00:00'),(136,'Hazel','Philtanker','HPHILTAN','650.127.1634','ST_CLERK',2200.00,NULL,122,50,'2002-12-23 00:00:00'),(137,'Renske','Ladwig','RLADWIG','650.121.1234','ST_CLERK',3600.00,NULL,123,50,'2002-12-23 00:00:00'),(138,'Stephen','Stiles','SSTILES','650.121.2034','ST_CLERK',3200.00,NULL,123,50,'2002-12-23 00:00:00'),(139,'John','Seo','JSEO','650.121.2019','ST_CLERK',2700.00,NULL,123,50,'2002-12-23 00:00:00'),(140,'Joshua','Patel','JPATEL','650.121.1834','ST_CLERK',2500.00,NULL,123,50,'2002-12-23 00:00:00'),(141,'Trenna','Rajs','TRAJS','650.121.8009','ST_CLERK',3500.00,NULL,124,50,'2002-12-23 00:00:00'),(142,'Curtis','Davies','CDAVIES','650.121.2994','ST_CLERK',3100.00,NULL,124,50,'2002-12-23 00:00:00'),(143,'Randall','Matos','RMATOS','650.121.2874','ST_CLERK',2600.00,NULL,124,50,'2002-12-23 00:00:00'),(144,'Peter','Vargas','PVARGAS','650.121.2004','ST_CLERK',2500.00,NULL,124,50,'2002-12-23 00:00:00'),(145,'John','Russell','JRUSSEL','011.44.1344.429268','SA_MAN',14000.00,0.40,100,80,'2002-12-23 00:00:00'),(146,'Karen','Partners','KPARTNER','011.44.1344.467268','SA_MAN',13500.00,0.30,100,80,'2002-12-23 00:00:00'),(147,'Alberto','Errazuriz','AERRAZUR','011.44.1344.429278','SA_MAN',12000.00,0.30,100,80,'2002-12-23 00:00:00'),(148,'Gerald','Cambrault','GCAMBRAU','011.44.1344.619268','SA_MAN',11000.00,0.30,100,80,'2002-12-23 00:00:00'),(149,'Eleni','Zlotkey','EZLOTKEY','011.44.1344.429018','SA_MAN',10500.00,0.20,100,80,'2002-12-23 00:00:00'),(150,'Peter','Tucker','PTUCKER','011.44.1344.129268','SA_REP',10000.00,0.30,145,80,'2014-03-05 00:00:00'),(151,'David','Bernstein','DBERNSTE','011.44.1344.345268','SA_REP',9500.00,0.25,145,80,'2014-03-05 00:00:00'),(152,'Peter','Hall','PHALL','011.44.1344.478968','SA_REP',9000.00,0.25,145,80,'2014-03-05 00:00:00'),(153,'Christopher','Olsen','COLSEN','011.44.1344.498718','SA_REP',8000.00,0.20,145,80,'2014-03-05 00:00:00'),(154,'Nanette','Cambrault','NCAMBRAU','011.44.1344.987668','SA_REP',7500.00,0.20,145,80,'2014-03-05 00:00:00'),(155,'Oliver','Tuvault','OTUVAULT','011.44.1344.486508','SA_REP',7000.00,0.15,145,80,'2014-03-05 00:00:00'),(156,'Janette','K_ing','JKING','011.44.1345.429268','SA_REP',10000.00,0.35,146,80,'2014-03-05 00:00:00'),(157,'Patrick','Sully','PSULLY','011.44.1345.929268','SA_REP',9500.00,0.35,146,80,'2014-03-05 00:00:00'),(158,'Allan','McEwen','AMCEWEN','011.44.1345.829268','SA_REP',9000.00,0.35,146,80,'2014-03-05 00:00:00'),(159,'Lindsey','Smith','LSMITH','011.44.1345.729268','SA_REP',8000.00,0.30,146,80,'2014-03-05 00:00:00'),(160,'Louise','Doran','LDORAN','011.44.1345.629268','SA_REP',7500.00,0.30,146,80,'2014-03-05 00:00:00'),(161,'Sarath','Sewall','SSEWALL','011.44.1345.529268','SA_REP',7000.00,0.25,146,80,'2014-03-05 00:00:00'),(162,'Clara','Vishney','CVISHNEY','011.44.1346.129268','SA_REP',10500.00,0.25,147,80,'2014-03-05 00:00:00'),(163,'Danielle','Greene','DGREENE','011.44.1346.229268','SA_REP',9500.00,0.15,147,80,'2014-03-05 00:00:00'),(164,'Mattea','Marvins','MMARVINS','011.44.1346.329268','SA_REP',7200.00,0.10,147,80,'2014-03-05 00:00:00'),(165,'David','Lee','DLEE','011.44.1346.529268','SA_REP',6800.00,0.10,147,80,'2014-03-05 00:00:00'),(166,'Sundar','Ande','SANDE','011.44.1346.629268','SA_REP',6400.00,0.10,147,80,'2014-03-05 00:00:00'),(167,'Amit','Banda','ABANDA','011.44.1346.729268','SA_REP',6200.00,0.10,147,80,'2014-03-05 00:00:00'),(168,'Lisa','Ozer','LOZER','011.44.1343.929268','SA_REP',11500.00,0.25,148,80,'2014-03-05 00:00:00'),(169,'Harrison','Bloom','HBLOOM','011.44.1343.829268','SA_REP',10000.00,0.20,148,80,'2014-03-05 00:00:00'),(170,'Tayler','Fox','TFOX','011.44.1343.729268','SA_REP',9600.00,0.20,148,80,'2014-03-05 00:00:00'),(171,'William','Smith','WSMITH','011.44.1343.629268','SA_REP',7400.00,0.15,148,80,'2014-03-05 00:00:00'),(172,'Elizabeth','Bates','EBATES','011.44.1343.529268','SA_REP',7300.00,0.15,148,80,'2014-03-05 00:00:00'),(173,'Sundita','Kumar','SKUMAR','011.44.1343.329268','SA_REP',6100.00,0.10,148,80,'2014-03-05 00:00:00'),(174,'Ellen','Abel','EABEL','011.44.1644.429267','SA_REP',11000.00,0.30,149,80,'2014-03-05 00:00:00'),(175,'Alyssa','Hutton','AHUTTON','011.44.1644.429266','SA_REP',8800.00,0.25,149,80,'2014-03-05 00:00:00'),(176,'Jonathon','Taylor','JTAYLOR','011.44.1644.429265','SA_REP',8600.00,0.20,149,80,'2014-03-05 00:00:00'),(177,'Jack','Livingston','JLIVINGS','011.44.1644.429264','SA_REP',8400.00,0.20,149,80,'2014-03-05 00:00:00'),(178,'Kimberely','Grant','KGRANT','011.44.1644.429263','SA_REP',7000.00,0.15,149,NULL,'2014-03-05 00:00:00'),(179,'Charles','Johnson','CJOHNSON','011.44.1644.429262','SA_REP',6200.00,0.10,149,80,'2014-03-05 00:00:00'),(180,'Winston','Taylor','WTAYLOR','650.507.9876','SH_CLERK',3200.00,NULL,120,50,'2014-03-05 00:00:00'),(181,'Jean','Fleaur','JFLEAUR','650.507.9877','SH_CLERK',3100.00,NULL,120,50,'2014-03-05 00:00:00'),(182,'Martha','Sullivan','MSULLIVA','650.507.9878','SH_CLERK',2500.00,NULL,120,50,'2014-03-05 00:00:00'),(183,'Girard','Geoni','GGEONI','650.507.9879','SH_CLERK',2800.00,NULL,120,50,'2014-03-05 00:00:00'),(184,'Nandita','Sarchand','NSARCHAN','650.509.1876','SH_CLERK',4200.00,NULL,121,50,'2014-03-05 00:00:00'),(185,'Alexis','Bull','ABULL','650.509.2876','SH_CLERK',4100.00,NULL,121,50,'2014-03-05 00:00:00'),(186,'Julia','Dellinger','JDELLING','650.509.3876','SH_CLERK',3400.00,NULL,121,50,'2014-03-05 00:00:00'),(187,'Anthony','Cabrio','ACABRIO','650.509.4876','SH_CLERK',3000.00,NULL,121,50,'2014-03-05 00:00:00'),(188,'Kelly','Chung','KCHUNG','650.505.1876','SH_CLERK',3800.00,NULL,122,50,'2014-03-05 00:00:00'),(189,'Jennifer','Dilly','JDILLY','650.505.2876','SH_CLERK',3600.00,NULL,122,50,'2014-03-05 00:00:00'),(190,'Timothy','Gates','TGATES','650.505.3876','SH_CLERK',2900.00,NULL,122,50,'2014-03-05 00:00:00'),(191,'Randall','Perkins','RPERKINS','650.505.4876','SH_CLERK',2500.00,NULL,122,50,'2014-03-05 00:00:00'),(192,'Sarah','Bell','SBELL','650.501.1876','SH_CLERK',4000.00,NULL,123,50,'2014-03-05 00:00:00'),(193,'Britney','Everett','BEVERETT','650.501.2876','SH_CLERK',3900.00,NULL,123,50,'2014-03-05 00:00:00'),(194,'Samuel','McCain','SMCCAIN','650.501.3876','SH_CLERK',3200.00,NULL,123,50,'2014-03-05 00:00:00'),(195,'Vance','Jones','VJONES','650.501.4876','SH_CLERK',2800.00,NULL,123,50,'2014-03-05 00:00:00'),(196,'Alana','Walsh','AWALSH','650.507.9811','SH_CLERK',3100.00,NULL,124,50,'2014-03-05 00:00:00'),(197,'Kevin','Feeney','KFEENEY','650.507.9822','SH_CLERK',3000.00,NULL,124,50,'2014-03-05 00:00:00'),(198,'Donald','OConnell','DOCONNEL','650.507.9833','SH_CLERK',2600.00,NULL,124,50,'2014-03-05 00:00:00'),(199,'Douglas','Grant','DGRANT','650.507.9844','SH_CLERK',2600.00,NULL,124,50,'2014-03-05 00:00:00'),(200,'Jennifer','Whalen','JWHALEN','515.123.4444','AD_ASST',4400.00,NULL,101,10,'2016-03-03 00:00:00'),(201,'Michael','Hartstein','MHARTSTE','515.123.5555','MK_MAN',13000.00,NULL,100,20,'2016-03-03 00:00:00'),(202,'Pat','Fay','PFAY','603.123.6666','MK_REP',6000.00,NULL,201,20,'2016-03-03 00:00:00'),(203,'Susan','Mavris','SMAVRIS','515.123.7777','HR_REP',6500.00,NULL,101,40,'2016-03-03 00:00:00'),(204,'Hermann','Baer','HBAER','515.123.8888','PR_REP',10000.00,NULL,101,70,'2016-03-03 00:00:00'),(205,'Shelley','Higgins','SHIGGINS','515.123.8080','AC_MGR',12000.00,NULL,101,110,'2016-03-03 00:00:00'),(206,'William','Gietz','WGIETZ','515.123.8181','AC_ACCOUNT',8300.00,NULL,205,110,'2016-03-03 00:00:00');

/*Table structure for table `jobs` */

DROP TABLE IF EXISTS `jobs`;

CREATE TABLE `jobs` (
  `job_id` varchar(10) NOT NULL,
  `job_title` varchar(35) DEFAULT NULL,
  `min_salary` int(6) DEFAULT NULL,
  `max_salary` int(6) DEFAULT NULL,
  PRIMARY KEY (`job_id`)
) ENGINE=InnoDB DEFAULT CHARSET=gb2312;

/*Data for the table `jobs` */

insert  into `jobs`(`job_id`,`job_title`,`min_salary`,`max_salary`) values ('AC_ACCOUNT','Public Accountant',4200,9000),('AC_MGR','Accounting Manager',8200,16000),('AD_ASST','Administration Assistant',3000,6000),('AD_PRES','President',20000,40000),('AD_VP','Administration Vice President',15000,30000),('FI_ACCOUNT','Accountant',4200,9000),('FI_MGR','Finance Manager',8200,16000),('HR_REP','Human Resources Representative',4000,9000),('IT_PROG','Programmer',4000,10000),('MK_MAN','Marketing Manager',9000,15000),('MK_REP','Marketing Representative',4000,9000),('PR_REP','Public Relations Representative',4500,10500),('PU_CLERK','Purchasing Clerk',2500,5500),('PU_MAN','Purchasing Manager',8000,15000),('SA_MAN','Sales Manager',10000,20000),('SA_REP','Sales Representative',6000,12000),('SH_CLERK','Shipping Clerk',2500,5500),('ST_CLERK','Stock Clerk',2000,5000),('ST_MAN','Stock Manager',5500,8500);

/*Table structure for table `locations` */

DROP TABLE IF EXISTS `locations`;

CREATE TABLE `locations` (
  `location_id` int(11) NOT NULL AUTO_INCREMENT,
  `street_address` varchar(40) DEFAULT NULL,
  `postal_code` varchar(12) DEFAULT NULL,
  `city` varchar(30) DEFAULT NULL,
  `state_province` varchar(25) DEFAULT NULL,
  `country_id` varchar(2) DEFAULT NULL,
  PRIMARY KEY (`location_id`)
) ENGINE=InnoDB AUTO_INCREMENT=3201 DEFAULT CHARSET=gb2312;

/*Data for the table `locations` */

insert  into `locations`(`location_id`,`street_address`,`postal_code`,`city`,`state_province`,`country_id`) values (1000,'1297 Via Cola di Rie','00989','Roma',NULL,'IT'),(1100,'93091 Calle della Testa','10934','Venice',NULL,'IT'),(1200,'2017 Shinjuku-ku','1689','Tokyo','Tokyo Prefecture','JP'),(1300,'9450 Kamiya-cho','6823','Hiroshima',NULL,'JP'),(1400,'2014 Jabberwocky Rd','26192','Southlake','Texas','US'),(1500,'2011 Interiors Blvd','99236','South San Francisco','California','US'),(1600,'2007 Zagora St','50090','South Brunswick','New Jersey','US'),(1700,'2004 Charade Rd','98199','Seattle','Washington','US'),(1800,'147 Spadina Ave','M5V 2L7','Toronto','Ontario','CA'),(1900,'6092 Boxwood St','YSW 9T2','Whitehorse','Yukon','CA'),(2000,'40-5-12 Laogianggen','190518','Beijing',NULL,'CN'),(2100,'1298 Vileparle (E)','490231','Bombay','Maharashtra','IN'),(2200,'12-98 Victoria Street','2901','Sydney','New South Wales','AU'),(2300,'198 Clementi North','540198','Singapore',NULL,'SG'),(2400,'8204 Arthur St',NULL,'London',NULL,'UK'),(2500,'Magdalen Centre, The Oxford Science Park','OX9 9ZB','Oxford','Oxford','UK'),(2600,'9702 Chester Road','09629850293','Stretford','Manchester','UK'),(2700,'Schwanthalerstr. 7031','80925','Munich','Bavaria','DE'),(2800,'Rua Frei Caneca 1360 ','01307-002','Sao Paulo','Sao Paulo','BR'),(2900,'20 Rue des Corps-Saints','1730','Geneva','Geneve','CH'),(3000,'Murtenstrasse 921','3095','Bern','BE','CH'),(3100,'Pieter Breughelstraat 837','3029SK','Utrecht','Utrecht','NL'),(3200,'Mariano Escobedo 9991','11932','Mexico City','Distrito Federal,','MX');

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

基础查询

语法：

select 查询列表

from 表名

特点：

查询列表可以是：表中的字段、常量值、表达式、函数
查询的结果是一个虚拟的表格

测试：

# 1. 查询表中的字段
select last_name
from employees;
# 2. 查询表中的多个字段
select last_name, salary, email
from employees;
# 3. 查询表中的所有字段
select employee_id,
       first_name,
       last_name,
       email,
       phone_number,
       job_id,
       salary,
       commission_pct,
       manager_id,
       department_id,
       hiredate
from employees;

select *
from employees;

# 4. 查询常量值
select 100;
select 'john';

# 5. 查询表达式
select 100 % 98;

# 6. 查询函数
select VERSION();

# 7. 起别名
# 方式1 使用as
select 100 % 98 AS 结果;
select last_name AS 姓, first_name AS 名
from employees;
# 方式2 使用空格
select last_name 姓, first_name 名
from employees;
# 案例：查询salary，显示结果为out put
select salary as "out put"
from employees;

# 8. 去重
# 案例：查询员工表中涉及到的所有部门编号
select distinct department_id
from employees;

# 9. 加号（+）的作用
/*
 java中的+号：
 ①：运算符，两个操作数都为数值型
 ②：连接符，只要有一个操作数为字符串

 mysql中的+号
 仅仅有一个功能，就是运算符
 select 100+90; 两个操作数为数值型，则做加法运算
 select '123'+90; 其中一方为字符型，试图将字符型数值转换成数值型，如果转换成功，则继续做加法运算
 select 'john'+90; 如果转换失败，则将字符型转换为0
 select null+10; 只要其中一方为null，则结果肯定为null
 */
# 案例：查询员工名和姓连接成一个字段，并显示为姓名
select CONCAT('a', 'b', 'c') AS 结果;
select concat(last_name, first_name) as 姓名
from employees;

条件查询

语法：

select 查询列表

from 表名

where 筛选条件;

分类：

按条件表达式筛选

条件运算符：> < = != <> >= <=
按逻辑表达式筛选

逻辑运算符：&& || ! and or not

作用：用于连接条件表达式
模糊查询

like

between and

in

is null
安全等于：<=>可以判断null值也可以判断普通数值

测试：

# 条件查询
# 一、按条件表达式筛选
# 案例1：查询工资>12000的员工信息
select *
from employees
where salary > 12000;

# 案例2：查询部门编号不等于90号的员工名和部门编号 可以用<>或者!=
select last_name, department_id
from employees
where department_id <> 90;

# 二、按逻辑表达式筛选
# 案例1：查询工资在10000到20000之间的员工名、工资及奖金
select last_name, salary, commission_pct
from employees
where salary >= 10000
  and salary <= 20000;

# 案例2：查询部门编号不是在90到110之间，或者工资高于15000的员工信息
select *
from employees
where department_id < 90
   OR department_id > 110
   OR salary > 15000;

select *
from employees
where NOT (department_id >= 90 AND department_id <= 110)
   OR salary > 15000;

# 三、模糊查询
/*
    like:
    通配符：
        %：任意多个字符
        _：任意单个字符

 */
# 案例1：查询员工名中包含字符a的员工信息
select *
from employees
where last_name like '%a%';

# 案例2：查询员工名中第三个字符为n，第五个字符为l的员工名和工资
select last_name, salary
from employees
where last_name like '__n_l%';

# 案例3：查询员工名中第二个字符为_的员工名（转义字符）
# 方式1：默认\转义
select last_name
from employees
where last_name like '_\_%';
# 方式2：指定转义字符$
select last_name
from employees
where last_name like '_$_%' escape '$';

/*
     between and
     ①：使用between and 可以提高语句的简洁度
     ②：包含临界值
     ③：两个临界值不要调换顺序
 */
# 案例1：查询员工编号在100到120之间的员工信息
select *
from employees
where employee_id >= 100
  AND employee_id <= 120;

select *
from employees
where employee_id between 100 AND 120;

/*
    in
    用于判断某字段的值是否属于in列表中的某一项
    ①：使用in提高语句简洁度
    ②：in列表的值类型必须统一或兼容
    ③：
 */
# 案例：查询员工的工种编号是 IT_PROG、AD_VP、AD_PRES中的一个的员工名和工种编号
select last_name, job_id
from employees
where job_id in ('IT_PROG', 'AD_VP', 'AD_PRES');

/*
    is null / is not null
    = 或者 <> 不能用于判断null值
 */
# 案例1：查询没有奖金的员工名和奖金率
select last_name, commission_pct
from employees
where commission_pct is NULL;

/*
    安全等于    <=> 可以判断null值
 */
# 案例1：查询没有奖金的员工名和奖金率
select last_name, commission_pct
from employees
where commission_pct <=> null;
# 案例2：查询工资为12000的员工信息
select last_name, salary
from employees
where salary <=> 12000;

# 综合案例：
# 1. 查询工资大于12000的员工姓名和工资
select last_name, salary
from employees emp
where emp.salary > 12000;
# 2. 查询员工号为176的员工的姓名和部门号以及年薪
select last_name, department_id, salary * 12 * (1 + IFNULL(commission_pct, 0)) 年薪
from employees emp
where emp.employee_id = 176;
# 3. 选择工资不在5000到12000的员工的姓名和工资
select emp.last_name, emp.salary
from employees emp
where emp.salary not between 5000 and 12000;
# 4. 选择在20或50号部门工作的员工姓名和部门号
select emp.last_name, emp.department_id
from employees emp
where emp.employee_id between 20 and 50;
# 5. 选择公司中没有管理者的员工姓名及job_id
select emp.last_name, emp.job_id
from employees emp
where emp.manager_id is null;
# 6. 选择公司中有奖金的员工姓名、工资和奖金级别
select emp.last_name, emp.salary, emp.commission_pct
from employees emp
where emp.commission_pct is not null;
# 7. 选择员工姓名的第三个字母是a的员工姓名
select emp.last_name
from employees emp
where emp.last_name like '__a%';
# 8. 选择姓名中有字母a和e的员工姓名
select emp.last_name
from employees emp
where emp.last_name like '%a%'
   OR emp.last_name like '%e%';
# 9. 显示出表employee中first_name以'e'结尾的员工信息
select first_name, last_name
from employees
where first_name like '%e';
# 10. 显示出employee中部门编号在80-100之间的姓名和职位
select emp.last_name, emp.job_id
from employees emp
where emp.department_id between 80 and 100;
# 11. 显示出employee的manager_id是100,101,110的员工姓名、职位
select emp.last_name, emp.job_id
from employees emp
where emp.manager_id in (100, 101, 110);

测试题

# 一、查询没有奖金，工资小于18000的salary、last_name
select emp.salary, emp.last_name
from employees emp
where emp.commission_pct is null
  AND emp.salary < 1800;
# 二、 查询employees表中，job_id不为“IT”或者工资为12000的员工信息
select emp.last_name,emp.job_id,emp.salary
from employees emp
where emp.job_id != 'IT' OR emp.salary = 12000;
# 三、 查看部门departments表的结构
desc departments;
# 四、查询部门departments表中涉及到了哪些位置编号
select distinct location_id
from departments;
/*
 五、 经典面试题：
 试问： select * from employees
        和  select * from employees where commission_pct like '%%" and last_name like '%%';
        结果是否一样？说明原因
 */
select *
from employees;
select *
from employees where commission_pct like '%%' and last_name like '%%';
# 答案是不一样，如果判断的值里有null值，则会不一样，如果都是or关键字就一样；

排序查询

语法：

select 查询列表

from 表

【where 筛选条件】

order by 排序列表 asc(升序默认)|desc(降序)

支持按表达式排序、按别名排序、按函数排序、多个字段排序

测试：

# 排序查询
use myemployees;
# 案例1：查询员工信息，要求工资从高到低排序
select *
from employees emp
order by emp.salary desc;

# 案例2：查询部门编号>=90的员工信息，按入职时间的先后进行排序【添加了筛选条件】
select *
from employees emp
where emp.department_id >= 90
order by hiredate asc;

# 案例3：按年薪的高低显示员工的信息和年薪【按表达式排序】
select emp.*, emp.salary * 12 * (1 + ifnull(emp.commission_pct, 0)) year_salary
from employees emp
order by emp.salary * 12 * (1 + ifnull(emp.commission_pct, 0)) desc;

# 案例4：按年薪的高低显示员工的信息和年薪【按别名排序】
select emp.*, emp.salary * 12 * (1 + ifnull(emp.commission_pct, 0)) year_salary
from employees emp
order by year_salary desc;

# 案例5：按姓名的长度显示员工的姓名和工资【按函数排序】
select length(last_name) 字节长度, last_name, salary
from employees
order by 字节长度 desc;

# 案例6：查询员工信息，要求先按工资排序[升序]，再按员工编号排序[降序]【按多个字段排序】
select *
from employees
order by salary, employee_id desc;

测试题

# 测试
# 1. 查询员工的姓名和部门号以及年薪，按年薪降序、姓名升序
select last_name, department_id, salary * 12 * (1 + ifnull(commission_pct, 0)) 年薪
from employees
order by 年薪 desc, last_name asc;
# 2. 选择工资不再8000到17000的员工的姓名和工资，按工资降序
select last_name, salary
from employees e
where e.salary not between 8000 and 17000
order by salary desc;
# 3. 查询邮箱中包含e的员工信息，并先按邮箱的字节数降序，再按部门号升序
select *
from employees e
where e.email like '%e%'
order by length(e.email) desc, e.department_id;

常见函数

概念：类似于java中的方法，将一组逻辑语句封装在方法体中，对外暴露方法名

好处：

隐藏了实现细节
提高代码的重用性

**调用：**select 函数名(实参列表)【from表】;

特点：

叫什么（函数名）
干什么（函数功能）

分类：

单行函数

concat、length、ifnull等
分组函数

主要用于统计使用，又称为统计函数、聚合函数、组函数

字符函数

length

# 1. length()：获取参数值的字节个数，utf-8一个中文3个字节
select length('john');
select length('张三丰hahaha');
show variables like '%char%';

concat

# 2. concat 拼接字符串
select concat(last_name, '_', first_name) 姓名
from employees;

upper、lower

# 3. upper、lower 大小写转换
select upper('john');
select lower('JoHn');
select concat(upper(last_name), lower(first_name)) 姓名
from employees;

substr、substring

# 4. substr、substring 截取字符 4个重载，字符长度
select substr('李莫愁爱上了陆展元', 7) out_put;
select substr('李莫愁爱上了陆展元', 1, 3) out_put;
# 案例：姓名中首字符大写，其他字符小写，然后用下划线_拼接显示出来
select last_name, concat(upper(substr(last_name, 1, 1)), '_', lower(substr(last_name, 2))) 结果
from employees;

instr

# 5. instr：返回子串第一次出现的位置，如果找不到就返回0
select instr('杨不悔爱上了殷六侠', '殷六侠');

trim

# 6. trim：去前后空格
select length(trim('       张翠山     ')), trim('       张翠山     ') as out_put;
select trim('a' from 'aaaaaaaaaaaa张aaaaaaa翠山aaaaa') as out_put;

lpad、rpad

# 7. lpad：用指定的字符实现左填充指定长度，超过则截断
select lpad('殷素素',10,'*') as out_put;
# 8. rpad：用指定的字符实现左填充指定长度，超过则截断
select rpad('殷素素',12,'ab') as out_put;

replace

# 9. replace 所有都会替换
select replace('周芷若-张无忌爱上了周芷若','周芷若','赵敏') as out_put;

数学函数

round

# 1. round 四舍五入
select round(-1.65);
select round(1.567,2);

ceil

# 2. ceil 向上取整，返回>=该参数的最小整数
select ceil(1.002); # 2
select ceil(-1.002);# -1

floor

# 3. floor 向下取整，返回<=该参数的最大整数
select floor(9.99); #9
select floor(-9.99);# 10

truncate

# 4. truncate 截断    保留几位小数，直接截断
select truncate(1.65,1);

mod

# 5. mod取余  a%b a-a/b*b
select MOD(10,3);# 1
select mod (-10,3);# -1

日期函数

序号	格式符	功能
1	%Y	四位的年份
2	%y	两位的年份
3	%m	月份（01,02,03......11,12）
4	%c	月份（1,2,3......11,12）
5	%d	日（01,02,03......）
6	%H	小时（24小时制）
7	%h	小时（12小时制）
8	%i	分钟（00,01......59）
9	%s	秒（00,01......59）

now

# 1. now 返回当前系统日期+时间
select now();

curdate/current_date

# 2. curdate/current_date 返回当前系统日期，不包含时间
select curdate();
select current_date();

curtime/current_time

# 3. curtime/current_time 返回当前系统时间，不包含日期
select curtime();
select current_time();

year/month/day/hour/minute/second

# 4. year/month/day/hour/minute/second获取指定部分——年月日、时分秒
select year(now()) 年;
select month('1998-1-1') 年;
select year(hiredate) from employees;
select month(hiredate) from employees;
select MONTHNAME(hiredate) from employees;

str_to_date

# 5. str_to_date：将日期格式的字符转换成指定格式的日期
select str_to_date('1998-3-2 1','%Y-%c-%d %h');
# 案例：查询入职日期为1992-4-3的员工信息
select * from employees where hiredate='1992-4-3';
select * from employees where hiredate=str_to_date('4-3 1992','%c-%d %Y');

date_format

# 6. date_format：将日期转换成字符
select date_format(now(),'%Y年%m月%d日');
# 案例：查询有奖金的员工名和入职日期（xx月/xx日 xx年）
select last_name,DATE_FORMAT(hiredate,'%m月/%d日 %y年')
from employees where commission_pct is not null;

其他函数【补充】

version

# 1. 查看当前数据库版本
select version();

database

# 2. 查看当前所在数据库
select database();

user

# 3. 当面用户
select user();

流程控制函数【补充】

if

# 1. if函数：类似三目运算符   表达式1结果为true则返回表达式2的值，false则返回表达式3的值
select if(10<5,'真','假');
# 案例：有奖金则返回有，否则返回无
select last_name,commission_pct,if(commission_pct is null,'无奖金','有奖金')
from employees;

case

语法一：

case 要判断的字段或表达式

when 常量1 then 要显示的值1或语句1;

when 常量2 then 要显示的值2或语句2;

...

else 要显示的值n或语句n;

end

# 2. case函数的使用一：switch case的效果
/*
    案例：查询员工的工资，要求
    部门号=30，显示的工资为1.1倍
    部门号=40，显示的工资为1.2倍
    部门号=50，显示的工资为1.3倍
    其他部门，显示的工资为原工资
 */
select salary,
       department_id,
       case department_id when 30 then salary * 1.1 when 40 then salary * 1.2 when 50 then salary * 1.3 else salary end
from employees;

语法二：

case

when 条件1 then 要显示的值1或语句1;

when 条件2 then 要显示的值2或语句2;

...

else 要显示的值n或语句n;

end

# 3. case函数的使用二：类似于 if-else if-else
/*
    案例：查询员工的工资情况
    如果工资>20000，显示A级别
    如果工资>15000，显示B级别
    如果工资>10000，显示C级别
    否则，显示D级别
 */
select salary,
       case when salary > 20000 then 'A' when salary > 15000 then 'B' when salary > 10000 then 'C' else 'D' end
from employees;

综合测试

# 综合测试
# 1. 显示系统时间（注：日期+时间）
select now();
# 2. 查询员工号、姓名、工资、工资提高百分之20%之后的结果
select employee_id, last_name, salary, salary * 1.2
from employees;
# 3. 将员工的姓名按首字母排序，并写出姓名的长度
select substr(last_name, 1, 1) 首字符, last_name, length(last_name)
from employees
order by 首字符;
/*
  4. 做一个查询，产生下面的结果：
  <last_name>earns<salary>monthly but wants<salary*3>
 */
select CONCAT(last_name, ' earns ', salary, ' monthly but wants ', salary * 3)
from employees;
/*
  5. 使用case-when，按照下面条件
    job_id      grade
    AD_PRES     A
    ST_MAN      B
    IT_PROG     C
    SA_REP      D
    ST_CLERK    E
 */
select last_name,
       job_id,
       case
           when job_id = 'AD_PRES' then 'A'
           when job_id = 'ST_MAN' then 'B'
           when job_id = 'IT_PROG' then 'C'
           when job_id = 'SA_REP' then 'D'
           when job_id = 'ST_CLERK' then 'E'
           end AS grade
from employees;

分组函数

**功能：**用于统计使用，又称为聚合函数、统计函数、组函数

分类：

sum：求和
avg：平均值
max：最大值
min：最小值
count：计算个数

特点：

sum、avg一般用于处理数值型
max、min、count可以处理任何类型
以上函数都会自动忽略null值
可以和distinct搭配使用
count函数单独介绍
- count(字段)：可以统计单个字段行数（非null才会统计）
- count(*)：统计行数，只要有一行的一个字段不为空就会被统计，所以就是所有记录数
- count(1)：相当于临时加上一列，所有的值都为1，也用于统计行数；
- 效率：
  - MYISAM存储引擎下：count(*)效率最高
  - INNODB存储引擎下：count(*)和count(1)效率差不多，但是比count(字段)高一些；
和分组函数一同查询的字段有限制，一般要求是group by之后的字段

sum/avg/max/min/count使用

# 分组函数
use myemployees;

# 1. 简单使用
select sum(salary)
from employees;

select avg(salary)
from employees;

select min(salary)
from employees;

select max(salary)
from employees;

select count(*)
from employees e;

select sum(salary), avg(salary), max(salary), min(salary), count(salary)
from employees;

select sum(salary), round(avg(salary), 2), max(salary), min(salary), count(salary)
from employees;

# 2. 参数支持哪些类型
select sum(last_name), avg(last_name)
from employees;
select sum(hiredate), avg(hiredate)
from employees;
select max(last_name), min(last_name)
from employees;
select max(hiredate), min(hiredate)
from employees;
select count(commission_pct)
from employees;
select count(last_name)
from employees;

# 3. 是否忽略null值
select sum(commission_pct), avg(commission_pct), sum(commission_pct) / 35, sum(commission_pct) / 107
from employees;

select max(commission_pct), min(commission_pct)
from employees;

select count(commission_pct)
from employees;

# 4. 和distinct搭配使用
select sum(distinct salary), sum(salary)
from employees;

select count(distinct salary), count(salary)
from employees;

综合测试

# 综合测试
# 1. 查询公司员工工资的最大值、最小值、平均值、总和
select max(salary), min(salary), avg(salary), sum(salary)
from employees;
# 2. 查询员工表中的最大入职时间和最小入职时间的相差天数（DATEDIFF）
select max(hiredate),min(hiredate),DATEDIFF(max(hiredate),min(hiredate))
from employees;
# 3. 查询部门编号为90的员工个数
select count(*)
from employees
where department_id=90;

分组查询

比如查询每个部门的平均工资等操作，需要对部门进行分组；

语法：

select column,group_function(column)

from table

[where condition]

[group by group_by_expression]

[having condition]

[order by column]

明确：WHERE条件一定要放在FROM后面；

注意：

查询列表比较特殊，要求是分组函数或者group by后面出现的字段

特点：

分组查询中的筛选条件分为两类（数据源不同）
- 分组前筛选（原始表）where，在from后面，group by前面
- 分组后筛选（分组后的结果集）having，在group by后面
分组函数做条件肯定是放在having子句中；
能用分组前筛选的，优先考虑使用分组前筛选，性能更好
group by 子句支持单个字段分组、多个字段分组（多个字段之间用逗号隔开，没有顺序要求），表达式跟函数也支持（用的比较少）；
也可以添加排序，放在整个分组查询的最后；

简单的分组查询

# 案例1：查询每个工种的最高工资
select max(salary), job_id
from employees
group by job_id;

# 案例2：查询每个位置上的部门个数
select count(*), location_id
from departments
group by location_id;

添加分组前的筛选条件

# 案例1：查询邮箱中包含a字符的，每个部门的平均工资
select department_id, avg(salary)
from employees
where email like '%a'
group by department_id;

# 案例2：查询有奖金的每个领导手下员工的最高工资
select max(salary), manager_id
from employees
where commission_pct is not null
group by manager_id;

添加分组后的筛选条件

# 案例1：查询哪个部门的员工个数>2
# ①：查询每个部门的员工个数
select department_id, count(*)
from employees
group by department_id;
# ②：根据①得到的结果进行筛选，查询哪些部门的员工个数>2
select department_id, count(*)
from employees
group by department_id
having count(*) > 2;

# 案例2：查询每个工种有奖金的员工，且最高工资>12000的工种编号和最高工资
select job_id, max(salary)
from employees
where commission_pct is not null
group by job_id
having max(salary) > 12000;

# 案例3：领导编号>102的每个领导手下的最低工资>5000的领导编号是哪个，以及其最低工资
select manager_id, min(salary)
from employees
where manager_id > 102
group by manager_id
having min(salary) > 5000;

按表达式或函数分组

# 案例：按员工姓名的长度分组，查询每一组的员工个数，筛选员工个数>5的有哪些
select length(last_name), count(*)
from employees
group by length(last_name)
having count(*) > 5;

按多个字段分组

# 案例：查询每个部门每个工种的员工的平均工资
select department_id, job_id, avg(salary)
from employees
group by department_id, job_id;

添加排序

## 案例：查询每个部门每个工种的员工的平均工资，部门不为null且平均工资高于10000，并且按平均工资的降序排序
select department_id, job_id, avg(salary)
from employees
where department_id is not null
group by department_id, job_id
having avg(salary) > 10000
order by avg(salary) desc;

综合测试

# 综合测试
# 1. 查询各个job_id的员工工资的最大值、最小值、平均值、总和，并按job_id排序
select job_id, max(salary), min(salary), avg(salary), sum(salary)
from employees
group by job_id
order by job_id;
# 2. 查询员工最高工资和最低工资的差距
select max(salary) - min(salary)
from employees;
# 3. 查询各个管理者手下员工的最低工资，其中最低工资不能低于6000，没有管理者的员工不计算在内
select manager_id, min(salary)
from employees
where manager_id is not null
group by manager_id
having min(salary) >= 6000;
# 4. 查询所有部门的编号，员工数量和工资平均值，并按平均工资降序排序
select department_id, count(*), avg(salary)
from employees
group by department_id;
# 5. 选择各个job_id的员工人数
select count(*),job_id
from employees
group by job_id;

连接查询

多表连接，当查询的字段来自多个表自然就要用到连接查询；

先导入表：

/*
SQLyog Ultimate v10.00 Beta1
MySQL - 5.7.18-log : Database - girls
*********************************************************************
*/


/*!40101 SET NAMES utf8 */;

/*!40101 SET SQL_MODE=''*/;

/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`girls` /*!40100 DEFAULT CHARACTER SET utf8 */;

USE `girls`;

/*Table structure for table `admin` */

DROP TABLE IF EXISTS `admin`;

CREATE TABLE `admin` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(10) NOT NULL,
  `password` varchar(10) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

/*Data for the table `admin` */

insert  into `admin`(`id`,`username`,`password`) values (1,'john','8888'),(2,'lyt','6666');

/*Table structure for table `beauty` */

DROP TABLE IF EXISTS `beauty`;

CREATE TABLE `beauty` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  `sex` char(1) DEFAULT '女',
  `borndate` datetime DEFAULT '1987-01-01 00:00:00',
  `phone` varchar(11) NOT NULL,
  `photo` blob,
  `boyfriend_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=13 DEFAULT CHARSET=utf8;

/*Data for the table `beauty` */

insert  into `beauty`(`id`,`name`,`sex`,`borndate`,`phone`,`photo`,`boyfriend_id`) values (1,'柳岩','女','1988-02-03 00:00:00','18209876577',NULL,8),(2,'苍老师','女','1987-12-30 00:00:00','18219876577',NULL,9),(3,'Angelababy','女','1989-02-03 00:00:00','18209876567',NULL,3),(4,'热巴','女','1993-02-03 00:00:00','18209876579',NULL,2),(5,'周冬雨','女','1992-02-03 00:00:00','18209179577',NULL,9),(6,'周芷若','女','1988-02-03 00:00:00','18209876577',NULL,1),(7,'岳灵珊','女','1987-12-30 00:00:00','18219876577',NULL,9),(8,'小昭','女','1989-02-03 00:00:00','18209876567',NULL,1),(9,'双儿','女','1993-02-03 00:00:00','18209876579',NULL,9),(10,'王语嫣','女','1992-02-03 00:00:00','18209179577',NULL,4),(11,'夏雪','女','1993-02-03 00:00:00','18209876579',NULL,9),(12,'赵敏','女','1992-02-03 00:00:00','18209179577',NULL,1);

/*Table structure for table `boys` */

DROP TABLE IF EXISTS `boys`;

CREATE TABLE `boys` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `boyName` varchar(20) DEFAULT NULL,
  `userCP` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

/*Data for the table `boys` */

insert  into `boys`(`id`,`boyName`,`userCP`) values (1,'张无忌',100),(2,'鹿晗',800),(3,'黄晓明',50),(4,'段誉',300);

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

分类：

按年代分类：
- sql92标准：mysql中仅支持内连接
- sql99标准【推荐】：mysql中支持内连接+外连接（左外和右外【Oracle支持全外连接】）+交叉连接
按功能分类：
- 内连接
  - 等值连接
  - 非等值连接
  - 自连接
- 外连接
  - 左外连接
  - 右外连接
  - 全外连接
- 交叉连接

sql92标准

注意：92语法只支持内连接，所以在连接条件为null的时候，可能会得不到想要的结果

多表等值连接的结果为多表的交集部分
n表连接，至少需要n-1个连接条件
多表的顺序没有要求
一般需要为表起别名
可以搭配前面介绍的所有子句使用，如排序、分组、筛选

等值连接

# 1. 等值连接
# 案例1：查询女神名和对应的男神名
select beauty.name, boys.boyName
from boys,
     beauty
where boys.id = beauty.boyfriend_id;

# 案例2：查询员工名和对应的部门名
select e.last_name, d.department_name
from employees e,
     departments d
where e.department_id = d.department_id;

# 案例3：查询员工名、工种编号、工种名
select e.last_name, e.job_id, j.job_title
from employees e,
     jobs j
where e.job_id = j.job_id;

# 案例4：查询有奖金的员工名、部门名【加筛选条件】
select e.last_name, d.department_name
from employees e,
     departments d
where e.department_id = d.department_id
  and e.commission_pct is not null;

# 案例5：查询城市中第二个字符为o的部门名和城市名【加筛选条件】
select d.department_name, l.city
from locations l,
     departments d
where d.location_id = l.location_id
  and l.city like '_o%';

# 案例6：查询每个城市的部门个数【加分组】
select city, count(*)
from locations l,
     departments d
where l.location_id = d.location_id
group by l.city;

# 案例7：查询有奖金的每个部门的部门名以及部门的领导编号,以及该部门的最低工资【加分组】
select d.department_name, d.manager_id, min(e.salary)
from employees e,
     departments d
where e.department_id = d.department_id
  and e.commission_pct is not null
group by d.department_name, d.manager_id;

# 案例8：查询每个工种的工种名和员工的个数，并且按员工的个数降序【加排序】
select j.job_title, count(*)
from jobs j,
     employees e
where e.job_id = j.job_id
group by j.job_title
order by count(*) desc;

# 案例9：查询员工名，部门名，所在城市【三表查询】
select e.last_name, d.department_name, l.city
from employees e,
     departments d,
     locations l
where e.department_id = d.department_id
  and d.location_id = l.location_id;

非等值连接

先建立一张工资等级表

create table job_grades
(
    grade_level varchar(3),
    lowest_sal  int,
    highest_sal int
);
insert into job_grades
values ('A', 1000, 2999),
       ('B', 3000, 5999),
       ('C', 6000, 9999),
       ('D', 10000, 14999),
       ('E', 15000, 24999),
       ('F', 25000, 40000);

# 2. 非等值连接
# 案例1：查询员工的工资和工资级别
select e.last_name, e.salary, j.grade_level
from employees e,
     job_grades j
where e.salary between j.lowest_sal and j.highest_sal;

自连接

# 3. 自连接
# 案例：查询员工名以及其上级的名字
select e.last_name, m.last_name
from employees e,
     employees m
where e.manager_id = m.employee_id;

综合测试

# 综合测试 1
# 1. 显示员工表中的最大工资、工资平均值
select max(salary), avg(salary)
from employees;
# 2. 查询员工表的employee_id，job_id，last_name，按department_id降序，salary升序
select employee_id, job_id, last_name
from employees
order by department_id desc, salary asc;
# 3. 查询员工表的job_id包含a和e的，并且a在e前面
select job_id
from employees
where job_id like '%a%e%';
/*
  4. 已知表student，有id（学号），name，gradeId（年级编号）
         表grade，有id（年级编号），name（年级名）
         表result，有id，score，studentNo（学号）
     要求查询姓名、年级名、成绩
    select s.name,g.name,r.score
    from student s,
         grade g,
         result r
    where s.gradeId = g.id and s.id = r.studentNo;
 */
# 5. 显示当前日期，以及去前后空格，截取子字符串的函数
select now(), trim('   123  '), substr('123456', 3);

# 综合测试 2
# 1. 显示所有员工的姓名，部门号和部门名称
select e.last_name, e.department_id, d.department_name
from employees e,
     departments d
where e.department_id = d.department_id;
# 2. 查询90号部门员工的job_id和90号部门location_id
select e.job_id, d.location_id
from employees e,
     departments d
where e.department_id = d.department_id
  and e.department_id = 90;
# 3. 选择所有有奖金的员工的 last_name,department_name,location_id,city
select e.last_name, d.department_name, d.location_id, l.city
from employees e,
     departments d,
     locations l
where e.department_id = d.department_id
  and d.location_id = l.location_id
  and e.commission_pct is not null;
# 4. 选择city在Toronto工作的员工的last_name,job_id,department_id,department_name
select e.last_name, e.job_id, d.department_id, d.department_name
from employees e,
     departments d,
     locations l
where e.department_id = d.department_id
  and d.location_id = l.location_id
  and l.city = 'Toronto';
# 5. 查询每个工种、每个部门的部门名、工种名和最低工资
select d.department_name, j.job_title, min(e.salary)
from employees e,
     departments d,
     jobs j
where e.department_id = d.department_id
  and e.job_id = j.job_id
group by j.job_id, d.department_name;
# 6. 查询每个国家下的部门个数大于2的国家编号
select l.country_id, count(*)
from locations l,
     departments d
where d.location_id = l.location_id
group by l.country_id
having count(*) > 2;
# 7. 选择指定员工的姓名、员工号、管理者的姓名和员工号
select e.last_name, e.employee_id, m.last_name, m.employee_id
from employees e,
     employees m
where e.manager_id = m.employee_id;

sql99标准

语法：

select 查询列表

from 表1 别名

【连接类型】join 表2

on 连接条件

【where 筛选条件】

【group by 分组】

【having 筛选条件】

【order by 排序列表】

分类：

内连接：inner

外连接：

左外：left 【outer】
右外：right 【outer】
全外：MySQL不支持，Oracle支持，full【outer】

交叉连接：cross

内连接

特点：

添加排序、分组、筛选
inner可以省略
筛选条件可以放在where后面，连接条件放在on后面，提高分离性，便于阅读
inner join连接和sql92语法中的等值连接效果是一样的，都是查询交集；

等值连接

# 二、sql99标准
# 1. 内连接
# 【内连接】 等值连接
# 案例1：查询员工名、部门名
select *
from employees e
         inner join departments d on e.department_id = d.department_id;
# 案例2：查询名字中包含e的员工名和工种名（筛选）
select e.last_name, j.job_title
from employees e
         inner join jobs j on e.job_id = j.job_id
where e.last_name like '%e%';
# 案例3：查询部门个数>3的城市名和部门个数（分组+筛选）
select l.city, count(*)
from departments d
         inner join locations l on d.location_id = l.location_id
group by l.city
having count(*) > 3;
# 案例4：查询哪个部门的部门员工个数>3的部门名和员工个数，并按个数降序（排序）
select d.department_name, count(*)
from employees e
         inner join departments d on e.department_id = d.department_id
group by e.department_id
having count(*) > 3
order by count(*) desc;
# 案例5：查询员工名、部门名、工种名，并按部门名降序
select e.last_name, d.department_name, j.job_title
from employees e
         inner join departments d on e.department_id = d.department_id
         inner join jobs j on e.job_id = j.job_id
order by d.department_name desc;

非等值连接

# 【内连接】非等值连接
# 案例1：查询员工的工资级别
select e.last_name, e.salary, jg.grade_level
from employees e
         inner join job_grades jg
                    on e.salary between jg.lowest_sal and jg.highest_sal;
# 案例2：查询每个工资级别的个数>20，并且按工资级别的降序
select count(*), jg.grade_level
from employees e
         inner join job_grades jg
                    on e.salary between jg.lowest_sal and jg.highest_sal
group by jg.grade_level
having count(*) > 20
order by jg.grade_level desc;

自连接

# 【内连接】自连接
# 案例1：查询员工的姓名、上级的名字
select e.last_name, m.last_name
from employees e
         inner join employees m on e.manager_id = m.employee_id;
# 案例2：查询姓名包含k的员工、上级的名字
select e.last_name, m.last_name
from employees e
         inner join employees m on e.manager_id = m.employee_id
where e.last_name like '%k%';

外连接

**应用场景：**用于查询一个表中有，另一个表中没有的记录

特点：

外连接的查询结果为主表中的所有记录，

如果从表中有和它匹配的，则显示匹配的值；

如果从表中没有匹配的，则显示null；

外连接查询结果 = 内连接结果 + 主表中有而从表中没有的记录
左外连接：left join，左边的是主表
右外连接：right join，右边的是主表
左外和右外交换两个表的顺序，可以实现同样的效果

# 2. 外连接
# 引入：查询男朋友不在男神表的女神名
use girls;
#           左外连接实现
select g.name
from beauty g
         left outer join boys b on g.boyfriend_id = b.id
where b.id is null;
#           右外连接实现
select g.name
from boys b
         right outer join beauty g on b.id = g.boyfriend_id
where b.id is null;

use myemployees;
# 案例1：查询哪个部门没有员工
select d.department_name, e.employee_id
from departments d
         left outer join employees e on d.department_id = e.department_id
where e.employee_id is null;

全外连接

内连接的结果+表1中有但表2中没有的+表2中有但表1中没有的

交叉连接

笛卡尔乘积

92语法与99语法的总结

**功能：**sql99支持的多

**可读性：**sql99实现连接条件和筛选条件的分离，可读性较高

Join连接总结

内连接【inner join】
左外连接【left outer join】
右外连接【right outer join】
全外连接【full outer join】（MySQL不支持，Oracle支持）
左外连接去除交集部分【left outer join+B.key为null】
右外连接去除交集部分【right outer join+A.key为null】
去除关联表交集部分

多表连接综合案例

# 综合案例
# 1. 查询编号>3的女神的男朋友信息，如果有则列出详细，如果没有则null填充
select g.*, b.*
from beauty g
         left outer join boys b
                         on g.boyfriend_id = b.id
where g.id > 3;

# 2. 查询哪个城市没有部门
use myemployees;
select l.city
from departments d
         left outer join locations l on l.location_id = d.location_id
where d.department_id is null;

# 3. 查询部门名为SAL或IT的员工信息
select e.last_name, d.department_id, d.department_name
from departments d
         left join employees e on e.department_id = d.department_id
where d.department_name = 'SAL'
   OR d.department_name = 'IT';

子查询

含义：

出现在其他语句中的select语句，称之为子查询或内查询；
外部的查询语句，称之为主查询或外查询

分类：

按子查询出现的位置

select后面
- 仅仅标量子查询
from后面
- 表子查询
where或having后面
- 标量子查询（单行）
- 列子查询（多行）
- 行子查询（多列多行）
exist后面（相关子查询）
- 表子查询

按结果集的行列数不同：

标量子查询（结果集只有一行一列）
列子查询（结果集只有一列多行）
行子查询（结果集只有一行多列）
表子查询（结果集一般为多行多列）

where或having后面

特点：

子查询放在小括号内
子查询一般放在条件的右侧
标量子查询，一般搭配着单行操作符使用（> < >= <= = <>）
列子查询，一般搭配多行操作符使用（in any some all）
子查询的执行优先于主查询查询，主查询的条件用到了子查询的结果

标量子查询(单行单列)

# 1. 标量子查询（单行子查询）
# 案例1：谁的工资比Abel高？
select e.last_name, e.salary
from employees e
where salary > (select e.salary
                from employees e
                where e.last_name = 'Abel');
# 案例2：返回job_id与141号员工相同，salary比143号员工多的员工姓名，job_id和工资
select e.last_name, e.job_id, e.salary
from employees e
where e.job_id = (select e.job_id from employees e where e.employee_id = 141)
  and e.salary > (select e.salary from employees e where e.employee_id = 143);
# 案例3：返回公司工资最少的员工的last_name,job_id和salary
select e.last_name, e.job_id, e.salary
from employees e
where e.salary = (select min(e.salary)
                  from employees e);
# 案例4：查询最低工资>50号部门最低工资的部门id和其最低工资
select e.department_id, min(salary)
from employees e
group by e.department_id
having min(e.salary) > (select min(salary)
                        from employees
                        where department_id = 50);

列子查询（多行单列）

返回多行
使用多行比较操作符

操作符	含义
IN / NOT IN	等于列表中的任意一个，若不在列表中的任意一个
ANY / SOME	和子查询返回的某一个值比较
ALL	和子查询返回的所有值比较

# 2. 列子查询（多行）
# 案例1：返回location_id是1400或1700的部门中所有员工的姓名
select e.last_name
from employees e
where e.department_id in (select d.department_id
                          from departments d
                          where d.location_id in (1400, 1700));
# 案例2：返回其他工种中比job_id为“IT_PROG”工种任一工资低的员工的员工号、姓名、job_id以及salary
select e.employee_id, e.last_name, e.job_id, e.salary
from employees e
where e.job_id != 'IT_PROG'
  AND e.salary < any (select distinct salary
                      from employees e
                      where e.job_id = 'IT_PROG');
select e.employee_id, e.last_name, e.job_id, e.salary
from employees e
where e.job_id != 'IT_PROG'
  AND e.salary < (select max(e.salary)
                  from employees e
                  where e.job_id = 'IT_PROG');
# 案例3：返回其他工种中比job_id为“IT_PROG"部门所有工资都低的员工的员工号、姓名、job_id以及salary
select e.employee_id, e.last_name, e.job_id, e.salary
from employees e
where e.job_id != 'IT_PROG'
  AND e.salary < all (
    select distinct e.salary
    from employees e
    where e.job_id = 'IT_PROG');
select e.employee_id, e.last_name, e.job_id, e.salary
from employees e
where e.job_id != 'IT_PROG'
  AND e.salary < (
    select min(e.salary)
    from employees e
    where e.job_id = 'IT_PROG');

行子查询（结果集一行多列或多行多列）

# 3. 行子查询（一行多列或多列多行）
# 案例1：查询员工编号最小并且工资最高的员工信息
select *
from employees
where employee_id = (select min(e.employee_id)
                     from employees e)
  AND salary = (select max(salary)
                from employees e);

select *
from employees e
where (e.employee_id, e.salary) = (select min(employee_id), max(salary) from employees e);

select后面

只支持标量子查询（一行一列）

# 二、select后面
# 案例1：查询每个部门的员工个数
select d.*,
       (
           select count(*)
           from employees e
           where e.department_id = d.department_id
       )
from departments d;
# 案例2：查询员工号为102的部门名
select e.employee_id, (select d.department_name from departments d where e.department_id = d.department_id)
from employees e
where e.employee_id = '102';

from后面

# 三、from后面
# 案例1：查询每个部门的平均工资的工资等级
select e.*, jg.grade_level
from (select avg(e.salary) salary, department_id
      from employees e
      group by e.department_id) e
         left join job_grades jg
                   on e.salary between jg.lowest_sal and jg.highest_sal;

exists后面（相关子查询）

语法：

exists (完整的查询语句)

**结果：**0或1

# 四、exists后面（相关子查询）
# 案例1：查询有员工名的部门名
# exists
select d.department_name
from departments d
where exists(select * from employees e where e.department_id = d.department_id)
# in
select d.department_name
from departments d
where d.department_id in (
    select e.department_id
    from employees e);

综合测试

# 综合测试
# 1. 查询和Zlotkey相同部门的员工姓名和工资
select e.last_name, e.salary
from employees e
where e.department_id = (select e.department_id from employees e where e.last_name = 'Zlotkey');
# 2. 查询工资比公司平均工资高的员工的员工号，姓名和工资
select e.employee_id, e.last_name, e.salary
from employees e
where e.salary > (select avg(salary)
                  from employees);
# 3. 查询各部门中工资比本部门平均工资高的员工的员工号、姓名和工资
select e.employee_id, e.last_name, e.salary, d.avg_salary, e.department_id
from employees e
         left join (select e.department_id, avg(e.salary) avg_salary
                    from employees e
                    group by e.department_id) d
                   on e.department_id = d.department_id
where e.salary > d.avg_salary;
# 4. 查询和姓名中包含字母u的员工在相同部门的员工的员工号和姓名
select e.employee_id, e.last_name
from employees e
where e.department_id in (
    select distinct e.department_id
    from employees e
    where e.last_name like '%u%')
  and e.last_name not like '%u%';
# 5. 查询在部门的location_id为1700的部门工作的员工的员工号
select e.employee_id
from employees e
where e.department_id in (
    select distinct d.department_id
    from departments d
    where d.location_id = 1700);
# 6. 查询管理者是K_ing的员工姓名和工资
select e.last_name, e.salary
from employees e
where e.manager_id in (select e.employee_id from employees e where e.last_name = 'K_ing');
# 7. 查询工资最高的员工的姓名，要求first_name和last_name显示为一列，列名为姓.名
select concat(e.first_name, '.', e.last_name)
from employees e
where e.salary = (select max(e.salary) max_salary from employees e);

子查询经典案例

查询工资最低的员工信息：last_name,salary
查询平均工资最低的部门信息
查询平均工资最低的部门信息和该部门的平均工资
查询平均工资最高的job信息
查询平均工资高于公司平均工资的部门有哪些？
查询出公司中所有manager的详细信息
各个部门中最高工资和最低工资的那个部门，最低工资是多少
查询平均工资最高的部门的manager的详细信息：last_name,department_id,email,salary

# 子查询经典案例
# 1. 查询工资最低的员工信息：last_name,salary
select last_name, salary
from employees e
where e.salary = (select min(salary) from employees);
# 2. 查询平均工资最低的部门信息
select *
from departments d
where d.department_id = (select e.department_id
                         from employees e
                         group by e.department_id
                         order by avg(e.salary)
                         limit 1);
# 3. 查询平均工资最低的部门信息和该部门的平均工资
select *
from departments d
         inner join (select e.department_id, avg(e.salary)
                     from employees e
                     group by e.department_id
                     order by avg(e.salary)
                     limit 1) a
                    on d.department_id = a.department_id;
# 4. 查询平均工资最高的job信息
select *
from jobs j
where j.job_id = (select e.job_id
                  from employees e
                  group by e.job_id
                  order by avg(e.salary) desc
                  limit 1);
# 5. 查询平均工资高于公司平均工资的部门有哪些？
select department_id, avg(salary)
from employees e
group by e.department_id
having avg(salary) > (select avg(salary) from employees);
# 6. 查询出公司中所有manager的详细信息
select distinct m.*
from employees e
         inner join employees m
                    on e.manager_id = m.employee_id;
# 7. 各个部门中最高工资中最低的那个部门，最低工资是多少
select max(e.salary),e.department_id
from employees e
group by e.department_id
order by max(e.salary) limit 1;
# 8. 查询平均工资最高的部门的manager的详细信息：last_name,department_id,email,salary
select e.*
from departments d
         right join (select e.department_id, avg(e.salary)
                     from employees e
                     group by e.department_id
                     order by avg(e.salary) desc
                     limit 1) s
                    on d.department_id = s.department_id
         left join employees e on e.employee_id = d.manager_id;

分页查询

语法：

select 查询列表

from 表

【join typejoin 表2

on 连接条件

where 筛选条件

group by 分组字段

having 分组后的筛选

order by 排序的字段】

limit offset,size；

offset：要显示条目的起始索引（从0开始）
size：要显示的条目个数

特点：

limit语句放在查询语句的最后，执行顺序也是最后
公式：

要显示的页数page，每页的条目数size

select 查询列表

from 表

limit (page-1)*size,size；

# 分页查询
# 案例1：查询前五条员工信息
use myemployees;
select *
from employees
limit 0,5;
select *
from employees
limit 5;
# 案例2：查询11-25条
select *
from employees
limit 10,15;
# 案例3：有奖金的员工信息，工资降序，前10名
select *
from employees e
where e.commission_pct is not null
order by e.salary desc
limit 10;

union联合查询

union：联合、合并，将多条查询语句的结果合并成一个结果；

语法：

查询语句1

union【all】

查询语句2

union【all】

......

应用场景：

要查询的结果来自于多个表，且多个表没有直接的连接关系，但查询的信息一致的时候；

特点：

要求多条查询语句的查询列数是一致的；
要求多条查询语句的查询的每一列的类型和顺序最好一致；
使用union会去重，使用union all会保留；

02_MySQL_DQL基本语法.md

02_MySQL_DQL基本语法

准备工作

基础查询

条件查询

测试题

排序查询

测试题

常见函数

字符函数

length

concat

upper、lower

substr、substring

instr

trim

lpad、rpad

replace

数学函数

round

ceil

floor

truncate

mod

日期函数

now

curdate/current_date

curtime/current_time

year/month/day/hour/minute/second

str_to_date

date_format

其他函数【补充】

version

database

user

流程控制函数【补充】

if

case

综合测试

分组函数

sum/avg/max/min/count使用

综合测试

分组查询

简单的分组查询

添加分组前的筛选条件

添加分组后的筛选条件

按表达式或函数分组

按多个字段分组

添加排序

综合测试

连接查询

sql92标准

等值连接

非等值连接

自连接

综合测试

sql99标准

内连接

等值连接

非等值连接

自连接

外连接

全外连接

交叉连接

92语法与99语法的总结

Join连接总结

多表连接综合案例

子查询

where或having后面

标量子查询(单行单列)

列子查询（多行单列）

行子查询（结果集一行多列或多行多列）

select后面

from后面

exists后面（相关子查询）

综合测试

子查询经典案例

分页查询

union联合查询

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