- -- 创建库
- CREATE DATABASE IF NOT EXISTS test04_dql;
- 切换到这个库
- USE test04_dql;
- -- 创建员工表
- DROP TABLE IF EXISTS `t_employee`;
- ---创建字段
- CREATE TABLE `t_employee` (
- `eid` INT NOT NULL COMMENT '员工编号',
- `ename` VARCHAR(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL COMMENT '员工姓名',
- `salary` DOUBLE NOT NULL COMMENT '薪资',
- `commission_pct` DECIMAL(3,2) DEFAULT NULL COMMENT '奖金比例',
- `birthday` DATE NOT NULL COMMENT '出生日期',
- `gender` ENUM('男','女') CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL DEFAULT '男' COMMENT '性别',
- `tel` CHAR(11) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL COMMENT '手机号码',
- `email` VARCHAR(32) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL COMMENT '邮箱',
- `address` VARCHAR(150) DEFAULT NULL COMMENT '地址',
- `work_place` SET('北京','深圳','上海','武汉') CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL DEFAULT '北京' COMMENT '工作地点'
- ) ENGINE=INNODB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
复制代码- //插入数据
- INSERT INTO `t_employee`(`eid`,`ename`,`salary`,`commission_pct`,`birthday`,`gender`,`tel`,`email`,`address`,`work_place`)
- VALUES (1,'孙洪亮',28000,'0.65','1980-10-08','男','13789098765','shl@atguigu.com','白庙村西街','北京,深圳'),
- (2,'何进',7001,'0.10','1984-08-03','男','13456732145','hj@atguigu.com','半截塔存','深圳,上海'),
- (3,'邓超远',8000,NULL,'1985-04-09','男','18678973456','dcy666@atguigu.com','宏福苑','北京,深圳,上海,武汉'),
- (4,'黄熙萌',9456,NULL,'1986-09-07','女','13609876789','hxm@atguigu.com','白庙村东街','深圳,上海,武汉'),
- (5,'陈浩',8567,NULL,'1978-08-02','男','13409876545','ch888@atguigu.com','回龙观','北京,深圳,上海'),
- (6,'韩庚年',12000,NULL,'1985-04-03','男','18945678986','hgn@atguigu.com','龙泽','深圳,上海'),
- (7,'贾宝玉',15700,'0.24','1982-08-02','男','15490876789','jby@atguigu.com','霍营','北京,武汉'),
- (8,'李晨熙',9000,'0.40','1983-03-02','女','13587689098','lc@atguigu.com','东三旗','深圳,上海,武汉'),
- (9,'李易峰',7897,NULL,'1984-09-01','男','13467676789','lyf@atguigu.com','西山旗','武汉'),
- (10,'陆风',8789,NULL,'1989-04-02','男','13689876789','lf@atguigu.com','天通苑一区','北京'),
- (11,'黄冰茹',15678,NULL,'1983-05-07','女','13787876565','hbr@atguigu.com','立水桥','深圳'),
- (12,'孙红梅',9000,NULL,'1986-04-02','女','13576234554','shm@atguigu.com','立城苑','上海'),
- (13,'李冰冰',18760,NULL,'1987-04-09','女','13790909887','lbb@atguigu.com','王府温馨公寓','北京'),
- (14,'谢吉娜',18978,'0.25','1990-01-01','女','13234543245','xjn@atguigu.com','园中园','上海,武汉'),
- (15,'董吉祥',8978,NULL,'1987-05-05','男','13876544333','djx@atguigu.com','小辛庄','北京,上海'),
- (16,'彭超越',9878,NULL,'1988-03-06','男','18264578930','pcy@atguigu.com','西二旗','深圳,武汉'),
- (17,'李诗雨',9000,NULL,'1990-08-09','女','18567899098','lsy@atguigu.com','清河','北京,深圳,武汉'),
- (18,'舒淇格',16788,'0.10','1978-09-04','女','18654565634','sqg@atguigu.com','名流花园','北京,深圳,武汉'),
- (19,'周旭飞',7876,NULL,'1988-06-13','女','13589893434','sxf@atguigu.com','小汤山','北京,深圳'),
- (20,'章嘉怡',15099,'0.10','1989-12-11','女','15634238979','zjy@atguigu.com','望都家园','北京'),
- (21,'白露',9787,NULL,'1989-09-04','女','18909876789','bl@atguigu.com','西湖新村','上海'),
- (22,'刘烨',13099,'0.32','1990-11-09','男','18890980989','ly@atguigu.com','多彩公寓','北京,上海'),
- (23,'陈纲',13090,NULL,'1990-02-04','男','18712345632','cg@atguigu.com','天通苑二区','深圳'),
- (24,'吉日格勒',10289,NULL,'1990-04-01','男','17290876543','jrgl@163.com','北苑','北京'),
- (25,'额日古那',9087,NULL,'1989-08-01','女','18709675645','ergn@atguigu.com','望京','北京,上海'),
- (26,'李红',5000,NULL,'1995-02-15','女','15985759663','lihong@atguigu.com','冠雅苑','北京'),
- (27,'周洲',8000,NULL,'1990-01-01','男','13574528569','zhouzhou@atguigu.com','冠华苑','北京,深圳');
复制代码 查询全部员工信息
- *代表全部信息都查出来
- SELECT * FROM t_employee;
复制代码
查询全部员工的名字和工资
- select 列名1,列名2 from 表名
- select ename,salary from t_employee
复制代码
查询全部员工的名字和工资,而且把名字修改为姓名
- select ename as 姓名,salary from t_employee
复制代码
去重满意列重复的数据
- 去除满足列名1和列名2一样的,然后去重
- select DISTINCT 列名1,列名2 from 表名
- 关键字 distinct 去除重复的
- select DISTINCT salary,gender from t_employee
复制代码
- select DISTINCT gender from t_employee
复制代码
制造一个常量列
- //意思就是查询的时候临时添加一个列,列名为aaa,这个列的数据都是'上谷歌'
- select 列名1,列名2,列数据 列名 from t_employee
- select ename as 姓名,salary,'上谷歌' aaa from t_employee
复制代码
- 查询所有员工姓名,月薪和年薪(年薪等于月薪*12,结果列字段为 姓名 , 月薪 , 年薪 )
复制代码- 中间空一格或者用as 都是起别名的意思
- select ename 姓名,salary 月薪,salary * 12 年薪 from t_employee
- select ename 姓名,salary 月薪,salary * 12 年薪 from t_employee
复制代码
- # 4. 查询所有员工姓名,月薪和年薪(年薪等于月薪*12,结果列字段为 姓名 , 月薪 , 年薪 )
复制代码- 这个关键字的意思就是假如这列的数据某行为null ,那么就变成填的第二个值
- ifnull(列名,变成的值)
- select ename as 姓名,salary as 月薪,ifnull(commission_pct,0) * salary '月奖金',((ifnull(commission_pct,0)) * salary + salary) as 月总 from t_employee
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- distinct 去重的意思,只保留一个
- 这句话的意思就是去重这一列,重复的然后只保留一个
- select distinct 列名 from 表名
- select distinct salary from t_employee
复制代码
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