MySQL单表查询练习

-- 单表查询练习
/* 素材
CREATE TABLE `emp`  (
  `empno` int(4) NOT NULL,
  `ename` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `job` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  `mgr` int(4) NULL DEFAULT NULL,
  `hiredate` date NOT NULL,
  `sai` int(255) NOT NULL,
  `comm` int(255) NULL DEFAULT NULL,
  `deptno` int(2) NOT NULL,
  PRIMARY KEY (`empno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

INSERT INTO `emp` VALUES (1001, '甘宁', '文员', 1013, '2000-12-17', 8000, NULL, 20);
INSERT INTO `emp` VALUES (1002, '黛绮丝', '销售员', 1006, '2001-02-20', 16000, 3000, 30);
INSERT INTO `emp` VALUES (1003, '殷天正', '销售员', 1006, '2001-02-22', 12500, 5000, 30);
INSERT INTO `emp` VALUES (1004, '刘备', '经理', 1009, '2001-04-02', 29750, NULL, 20);
INSERT INTO `emp` VALUES (1005, '谢逊', '销售员', 1006, '2001-09-28', 12500, 14000, 30);
INSERT INTO `emp` VALUES (1006, '关羽', '经理', 1009, '2001-05-01', 28500, NULL, 30);
INSERT INTO `emp` VALUES (1007, '张飞', '经理', 1009, '2001-09-01', 24500, NULL, 10);
INSERT INTO `emp` VALUES (1008, '诸葛亮', '分析师', 1004, '2007-04-19', 30000, NULL, 20);
INSERT INTO `emp` VALUES (1009, '曾阿牛', '董事长', NULL, '2001-11-17', 50000, NULL, 10);
INSERT INTO `emp` VALUES (1010, '韦一笑', '销售员', 1006, '2001-09-08', 15000, 0, 30);
INSERT INTO `emp` VALUES (1011, '周泰', '文员', 1006, '2007-05-23', 11000, NULL, 20);
INSERT INTO `emp` VALUES (1012, '程普', '文员', 1006, '2001-12-03', 9500, NULL, 30);
INSERT INTO `emp` VALUES (1013, '庞统', '分析师', 1004, '2001-12-03', 30000, NULL, 20);
INSERT INTO `emp` VALUES (1014, '黄盖', '文员', 1007, '2002-01-23', 13000, NULL, 10);
INSERT INTO `emp` VALUES (1015, '张三', '保洁员', 1001, '2013-05-01', 80000, 50000, 50);

*/

1. 查询出部门编号为30的所有员工

mysql> select * from emp where deptno=30;

 2. 所有销售员的姓名、编号和部门编号。

mysql> select ename,empno,deptno from emp where job='销售员';

3. 找出奖金高于工资的员工。

mysql> select * from emp where comm > sai;

4. 找出奖金高于工资60%的员工。

mysql> select * from emp where comm > sai*0.6;

5. 找出部门编号为10中所有经理，和部门编号为20中所有销售员的详细资料。

mysql> select * from emp where (job='经理' and deptno=10) or (job='销售员' and deptno=20);

6. 找出部门编号为10中所有经理，部门编号为20中所有销售员，还有即不是经理又不是销售员但其工资大或等于20000的所有员工详细资料。

mysql> select * from emp where (job='经理' and deptno=10)
    -> or (job='销售员'and deptno=20)
    -> or (job not in ("经理","销售员" ) and sai >= 20000);

 7. 无奖金或奖金低于1000的员工。

mysql> select * from emp where comm is null or comm < 1000;

8. 查询名字由三个字组成的员工。

mysql> select * from emp where ename like '___';

 9.查询2000年入职的员工。

mysql> select * from emp where year(hiredate)=2000;

 10. 查询所有员工详细信息，用编号升序排序

mysql> select * from emp order by empno;

11. 查询所有员工详细信息，用工资降序排序，如果工资相同使用入职日期升序排序

mysql> select * from emp order by sai desc,hiredate asc;

12.查询每个部门的平均工资

mysql> select deptno,avg(sai) from emp group by deptno;

 13.查询每个部门的雇员数量

mysql> select deptno,count(empno) from emp group by deptno;

 14.查询每种工作的最高工资、最低工资、人数

mysql> select job,max(sai),min(sai),count(empno) from emp group by job;