MySQL学习之一:基础查询,排序查询,条件查询!!!

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简介: MySQL学习之一:基础查询,排序查询,条件查询!!!   大学学的是sqlserver2008,出来才发现大多用的是MySQL,好在语法都是一样的,基础也就是有的。 先唠叨两句,为什么大多用MySQL呀,跨平台性,开源,部分收费,对于微软的数据库,只能运行在windos上,这也就是一个局限性了,我们要的是部署在服务器的数据库,也就是linux上部署数据库,虽说微软也有服务器上运行的系统,但大多还是在使用linux服务器系统。

MySQL学习之一:基础查询,排序查询,条件查询!!!

 

大学学的是sqlserver2008,出来才发现大多用的是MySQL,好在语法都是一样的,基础也就是有的。

先唠叨两句,为什么大多用MySQL呀,跨平台性,开源,部分收费,对于微软的数据库,只能运行在windos上,这也就是一个局限性了,我们要的是部署在服务器的数据库,也就是linux上部署数据库,虽说微软也有服务器上运行的系统,但大多还是在使用linux服务器系统。而MySQL是可以部署到Linux服务器系统的。

其他的数据库还有DB2,甲骨文的数据库。

我们在自己的电脑上安装MySQL,相当于c/s架构,服务器端是MySQL。

怎么说呢,安装自己去MySQL,建议是5.7,感觉5.5和5.6版本的安装费劲,

对于图形化我用的是SQLyog操作数据库。

从基础开始。

##数据库的好处
    1.持久化数据到本地
    2.可以实现结构化查询,方便管理
##数据库相关概念
    1、DB:数据库,保存一组有组织的数据的容器
    2、DBMS:数据库管理系统,又称为数据库软件(产品),用于管理DB中的数据
    3、SQL:结构化查询语言,用于和DBMS通信的语言

##数据库存储数据的特点
    1、将数据放到表中,表再放到库中
    2、一个数据库中可以有多个表,每个表都有一个的名字,用来标识自己。表名具有唯一性。
    3、表具有一些特性,这些特性定义了数据在表中如何存储,类似java中 “类”的设计。
    4、表由列组成,我们也称为字段。所有表都是由一个或多个列组成的,每一列类似java 中的”属性”
    5、表中的数据是按行存储的,每一行类似于java中的“对象”。


##MySQL产品的使用
###MySQL服务的启动和停止
    方式一:计算机——右击管理——服务
    方式二:通过管理员身份运行
    net start 服务名(启动服务)
    net stop 服务名(停止服务)


###MySQL服务的登录和退出   
    方式一:通过mysql自带的客户端
    只限于root用户

    方式二:通过windows自带的客户端
    登录:
    mysql 【-h主机名 -P端口号 】-u用户名 -p密码

    退出:
    exit或ctrl+C

###SQL语言的分类

    1、DQL语言:Data Query Language 数据查询语言  
            select

    2、DML语言:Data Multipulation Language 数据操作语言
            insert、update、delete
    3、DDL语言:Data Define Language 数据定义语言
            create、drop、alter
    4、DCL语言:Data Control Language数据控制语言
            TCL:Transaction Control Language事务控制语言
            commit、rollback


###MySQL语法规范

1.不区分大小写,建议关键字大写,表名和列名小写
2.每句命令的结尾使用分号

3.sql中的注释
    
    方式一:单行注释
            -- 注释文字
    方式二:单行注释
            #注释文字
    方式三:多行注释
            /*注释文字*/

4.每句命令,根据需要可以换行,但关键字或表名、列名不可以拆开




上代码:(就是关键字,语法,好在sql语言是个弱语言)

先从有歧义的开始(在具体的代码中也会再次提到)

 

DESC 加表名   获取表的结构,包含的字段(也就是列表名)等。

DESC 同时也是降序的关键字,这里不用弄混!!!

 

java中+的作用

1、加法运算

2、拼接

sql中+的作用

加法运算!!

特点:

①两个数值型相加,就是普通的加法运算

②如果其中一方为字符型,则试图将字符转换成数值,如果转换成功,则直接加法运算

如果转换失败,则将该字符转换成0,然后再加法运算

③如果其中一方为null,则结果肯定为null

千万不要搞混!!!!!!这也就引出除了,IFNULL的使用。

IFNULL(字段(列名),要替换的值)  当用CONTI  进行拼接时,要拼接的内容中存在null值时,则结果就为null了,这时候我们就需要使用IFNULL关键字了,如果字段为NULL,则用要替换的值替换,这里要注意要替换的值必须和字段规定的数据类型一致。



 

一)关系表达式

通过关系运算符组成的表达式:关系表达式

java中的判断相等时用==,而sql中是=

sql中不等于是<>,但是它是支持!=的

sql中的关系运算符:>   <   >=   <=   =    (!=   <>)

 

二)逻辑表达式

通过逻辑运算符组成的表达式:逻辑不是

sql中的逻辑运算符:and、or 、not   【&& || !】

一定要和Java中的区分开,

 

下面就可以开始基础的了!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!




例子中用到的数据库,自己可以去执行添加一下


/*
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 */;

 

常见的:

#显示该连接下所有的库

SHOW DATABASES;

#切换到指定的库

USE test;

#显示当前库中的所有表

SHOW TABLES ;

#显示指定库中的所有表

SHOW TABLES FROM mysql;

#查看指定表的结构

DESC student;

#查看当前服务器的版本

SELECT VERSION()



 

#进阶1:基础查询

/*

语法:

select 查询列表 from 表名;

特点:

1.查询的结果为一个虚拟表,并没有真实存在

2.查询列表可以是常量、字段、表达式、函数以及上述的组合

类似于 System.out.println("");

 

补充函数:

concat拼接

version查看版本

database查看当前打开的数据库

user查看当前的用户

ifnull判断某字段或表达式是否为null,如果为null则显示指定的值

 */
 

USE  myemployees;

#1.查询常量

/*

如果是数值型的常量,则不用引号

如果是字符型或日期型的常量,最好使用引号

*/


SELECT 'john';
SELECT 100;

 

#2.查询表达式

SELECT 100+99;

 

#3.查询函数(方法)


SELECT VERSION();-- 查看当前数据库服务的版本
SELECT DATABASE();-- 查看当前连接的数据库

 

#4.查询单个字段

SELECT last_name FROM employees ;

#5.查询多个字段

SELECT last_name,salary ,first_name FROM employees;

#6.查询所有字段

 

#方式一:

#方式二:使用 *

SELECT * FROM employees;

 

#【综合案例】查询 函数、字段、常量

 

SELECT USER(),last_name,salary*12 FROM employees;
 

#7.起别名

/*

别名值可以使用单引号或双引号引起来,也可以不引

如果别名值有特殊符号,则必须用引号引起来!

*/

 

#方式一:使用as

SELECT USER() AS '当前 用户'  ;

 


SELECT
    `employee_id`,
    `first_name`,
    `last_name`,
    `email`,
    `phone_number`,
    `job_id`,
    `salary`,
    `commission_pct`,
    `manager_id`,
    `department_id`,
    `hiredate`
FROM
    employees ;

#方式二:使用空格

 


SELECT USER() 当前用户;
 

#8.+连接符

/*

回顾:

java中+的作用

1、加法运算

2、拼接

sql中+的作用

加法运算!!

特点:

①两个数值型相加,就是普通的加法运算

②如果其中一方为字符型,则试图将字符转换成数值,如果转换成功,则直接加法运算

如果转换失败,则将该字符转换成0,然后再加法运算

③如果其中一方为null,则结果肯定为null

 


select 100+23;      结果 123
select 1.5+2;        结果3.5
select 'john'+100;   结果100
select '234'+100;  结果100
select null+null;   结果null

要知道当连接是,一但连接的元素中有null的,则结果则为null(一般对于+ 和concat).

*/


SELECT first_name+last_name FROM employees;
SELECT CONCAT(first_name,last_name) AS 姓名 FROM employees;



#进阶2:条件查询

/*

语法:

select 查询列表 from 表名

where 条件;
 

条件的形式:

 

一)关系表达式

通过关系运算符组成的表达式:关系表达式

sql中的关系运算符:> < >= <= = != <>

二)逻辑表达式

通过逻辑运算符组成的表达式:逻辑不是

sql中的逻辑运算符:and、or 、not   【&& || !】

三)模糊查询

like、between and、in、is null

*/

SELECT last_name,first_name,salary,email,department_id,job_id FROM employees;

#一、按关系表达式查询

#案例1:查询工资>10000的员工信息

SELECT * FROM employees WHERE salary>10000;

#案例2:查询 job_id不是'IT_PROG'的员工姓名、job_id、salary


SELECT last_name,job_id,salary
FROM employees
WHERE job_id<>'IT_PROG';
SELECT last_name,job_id,salary
FROM employees
WHERE NOT(job_id='IT_PROG');

 




 

#二、按逻辑表达式查询

#案例1:查询工资>10000并且小于20000的员工姓名、工资、年薪


SELECT last_name,salary,salary*12*(1+IFNULL(commission_pct,0)) AS 年薪 FROM employees
WHERE salary>10000 AND salary<20000;

 

#案例2:查询部门编号不在90到120之间的并且 工资>15000的员工信息


SELECT * FROM employees
WHERE NOT(department_id >=90 AND department_id<=120) AND salary>15000;

#三、模糊查询

 

#1、like

/*

like一般搭配通配符使用。

常见的通配符:

%:任意0个或多个字符

_:任意单个字符

*/

 

 

#案例1:查询员工信息表中姓名第一个字符为e的员工信息


SELECT * FROM employees
WHERE last_name LIKE 'e%';

#案例2:查询员工信息表中姓名第二个字符为e,第五个字符为a的员工信息

 


SELECT * FROM employees
WHERE last_name LIKE '_e__a%';

#案例3:查询姓名中前面字符为ernst的员工信息


SELECT * FROM employees
WHERE last_name LIKE 'ernst%';

 

#方式一:直接通过\进行转义

SELECT * FROM employees

WHERE last_name LIKE '_\_%';

 

#方式二:通过escape关键字指定转义字符

 

SELECT * FROM employees

WHERE last_name LIKE '_$_%' ESCAPE '$';

#2、between and

 

/*

特点:

①用于筛选某个字段或表达式是否在指定的区间范围

②等价于 使用逻辑表达式的效果,只是语法上更加简单

③两个区间值不能调换顺序

④两个区间值包含

>=左区间 and <=右区间

*/

#案例1:查询年薪在100000到200000的员工年薪和姓名


SELECT salary*12*(1+IFNULL(commission_pct,0)) 年薪,last_name 姓名
FROM employees
WHERE salary*12*(1+IFNULL(commission_pct,0)) BETWEEN 100000 AND 200000;

 #案例2:查询年薪不在100740到187200的员工年薪和姓名


SELECT salary*12*(1+IFNULL(commission_pct,0)) 年薪,last_name 姓名
FROM employees
WHERE salary*12*(1+IFNULL(commission_pct,0)) NOT BETWEEN 100740 AND 187200

#3、in

/*

说明:在...里面

特点:

①效果等价于 使用or连接,只是语法上更加的简洁

*/

 

#案例1:查询工种编号是IT_PROT或是ST_CLERK或是AD_VP的员工信息

#传统方式:

 


SELECT * FROM employees
WHERE job_id ='IT_PROG'
OR job_id = 'ST_CLERK'
OR job_id = 'AD_VP';

#in方式


SELECT * FROM employees
WHERE job_id NOT IN('IT_PROG','ST_CLERK','AD_VP');

#4、is null

#案例1:查询哪个员工没有奖金
 


SELECT * FROM employees
WHERE commission_pct IS NULL;

#案例2:查询哪个员工有奖金


SELECT * FROM employees
WHERE commission_pct IS NOT NULL;

#进阶3:排序查询

/*

语法:

 

select 查询列表

from 表名

where 条件

order by 排序列表 asc|desc;

 

特点:

1、asc代表升序,desc代表降序。默认是升序

2、查询列表可以是 单个字段、多个字段、函数、表达式、别名或上述的组合

 */
#1.按单个字段进行升序

 

#案例1:按工资从低到高排序


SELECT *
FROM employees
ORDER BY salary ;

#案例2:按工资从低到高排序


SELECT *
FROM employees
ORDER BY salary DESC;

#2.按多个字段排序

#案例1:部门编号>50的按工资从高到低排序,如果一样,再按frist_name升序


SELECT *
FROM employees
WHERE department_id>50
ORDER BY salary DESC,first_name ASC;

#3.按表达式排序

#案例:将姓名中包含e字符的年薪和姓名显示出来,并且按年薪进行降序


SELECT salary*12*(1+IFNULL(commission_pct,0)) 年薪,last_name
FROM employees
WHERE last_name LIKE '%e%'
ORDER BY salary*12*(1+IFNULL(commission_pct,0)) DESC;

#4.按别名排序

#案例:将姓名中包含e字符的年薪和姓名显示出来,并且按年薪进行降序


SELECT salary*12*(1+IFNULL(commission_pct,0)) 年薪,last_name
FROM employees
WHERE last_name LIKE '%e%'
ORDER BY 年薪 DESC;

#5.按函数排序

#案例:显示所有有奖金的员工姓名、奖金、姓名的长度,按姓名的长度从低到高排序


SELECT last_name,commission_pct ,LENGTH(last_name) 长度
FROM employees
WHERE commission_pct IS NOT NULL
ORDER BY LENGTH(last_name)

 原文地址https://blog.csdn.net/yuanmomoya/article/details/81912099

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