练习MySQL查询技巧-单表查询

访客 2023年07月13日 18:57 228 0

MySQL单表查询：

建表：

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;

mysql> desc emp;+----------+--------------+------+-----+---------+-------+| Field    | Type         | Null | Key | Default | Extra |+----------+--------------+------+-----+---------+-------+| empno    | int(4)       | NO   | PRI | NULL    |       || ename    | varchar(255) | YES  |     | NULL    |       || job      | varchar(255) | YES  |     | NULL    |       || mgr      | int(4)       | YES  |     | NULL    |       || hiredate | date         | NO   |     | NULL    |       || sai      | int(255)     | NO   |     | NULL    |       || comm     | int(255)     | YES  |     | NULL    |       || deptno   | int(2)       | NO   |     | NULL    |       |+----------+--------------+------+-----+---------+-------+

插入数据：

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

mysql> select * from emp;+-------+-----------+-----------+------+------------+-------+-------+--------+| empno | ename     | job       | mgr  | hiredate   | sai   | comm  | deptno |+-------+-----------+-----------+------+------------+-------+-------+--------+|  1001 | 甘宁      | 文员      | 1013 | 2000-12-17 |  8000 |  NULL |     20 ||  1002 | 黛绮丝    | 销售员    | 1006 | 2001-02-20 | 16000 |  3000 |     30 ||  1003 | 殷天正    | 销售员    | 1006 | 2001-02-22 | 12500 |  5000 |     30 ||  1004 | 刘备      | 经理      | 1009 | 2001-04-02 | 29750 |  NULL |     20 ||  1005 | 谢逊      | 销售员    | 1006 | 2001-09-28 | 12500 | 14000 |     30 ||  1006 | 关羽      | 经理      | 1009 | 2001-05-01 | 28500 |  NULL |     30 ||  1007 | 张飞      | 经理      | 1009 | 2001-09-01 | 24500 |  NULL |     10 ||  1008 | 诸葛亮    | 分析师    | 1004 | 2007-04-19 | 30000 |  NULL |     20 ||  1009 | 曾阿牛    | 董事长    | NULL | 2001-11-17 | 50000 |  NULL |     10 ||  1010 | 韦一笑    | 销售员    | 1006 | 2001-09-08 | 15000 |     0 |     30 ||  1011 | 周泰      | 文员      | 1006 | 2007-05-23 | 11000 |  NULL |     20 ||  1012 | 程普      | 文员      | 1006 | 2001-12-03 |  9500 |  NULL |     30 ||  1013 | 庞统      | 分析师    | 1004 | 2001-12-03 | 30000 |  NULL |     20 ||  1014 | 黄盖      | 文员      | 1007 | 2002-01-23 | 13000 |  NULL |     10 ||  1015 | 张三      | 保洁员    | 1001 | 2013-05-01 | 80000 | 50000 |     50 |+-------+-----------+-----------+------+------------+-------+-------+--------+

查询数据：

查询出部门编号为30的所有员工：

mysql> select * from emp where deptno=30;+-------+-----------+-----------+------+------------+-------+-------+--------+| empno | ename     | job       | mgr  | hiredate   | sai   | comm  | deptno |+-------+-----------+-----------+------+------------+-------+-------+--------+|  1002 | 黛绮丝    | 销售员    | 1006 | 2001-02-20 | 16000 |  3000 |     30 ||  1003 | 殷天正    | 销售员    | 1006 | 2001-02-22 | 12500 |  5000 |     30 ||  1005 | 谢逊      | 销售员    | 1006 | 2001-09-28 | 12500 | 14000 |     30 ||  1006 | 关羽      | 经理      | 1009 | 2001-05-01 | 28500 |  NULL |     30 ||  1010 | 韦一笑    | 销售员    | 1006 | 2001-09-08 | 15000 |     0 |     30 ||  1012 | 程普      | 文员      | 1006 | 2001-12-03 |  9500 |  NULL |     30 |+-------+-----------+-----------+------+------------+-------+-------+--------+

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';+-----------+-------+--------+| ename     | empno | deptno |+-----------+-------+--------+| 黛绮丝    |  1002 |     30 || 殷天正    |  1003 |     30 || 谢逊      |  1005 |     30 || 韦一笑    |  1010 |     30 |+-----------+-------+--------+

找出奖金高于工资的员工：

mysql> select * from emp where comm>sai;+-------+--------+-----------+------+------------+-------+-------+--------+| empno | ename  | job       | mgr  | hiredate   | sai   | comm  | deptno |+-------+--------+-----------+------+------------+-------+-------+--------+|  1005 | 谢逊   | 销售员    | 1006 | 2001-09-28 | 12500 | 14000 |     30 |+-------+--------+-----------+------+------------+-------+-------+--------+

找出奖金高于工资60%的员工：

mysql> select * from emp where comm > sai*0.6;+-------+--------+-----------+------+------------+-------+-------+--------+| empno | ename  | job       | mgr  | hiredate   | sai   | comm  | deptno |+-------+--------+-----------+------+------------+-------+-------+--------+|  1005 | 谢逊   | 销售员    | 1006 | 2001-09-28 | 12500 | 14000 |     30 ||  1015 | 张三   | 保洁员    | 1001 | 2013-05-01 | 80000 | 50000 |     50 |+-------+--------+-----------+------+------------+-------+-------+--------+

找出部门编号为10中所有经理，和部门编号为30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=30);+-------+-----------+-----------+------+------------+-------+-------+--------+| empno | ename     | job       | mgr  | hiredate   | sai   | comm  | deptno |+-------+-----------+-----------+------+------------+-------+-------+--------+|  1002 | 黛绮丝    | 销售员    | 1006 | 2001-02-20 | 16000 |  3000 |     30 ||  1003 | 殷天正    | 销售员    | 1006 | 2001-02-22 | 12500 |  5000 |     30 ||  1005 | 谢逊      | 销售员    | 1006 | 2001-09-28 | 12500 | 14000 |     30 ||  1007 | 张飞      | 经理      | 1009 | 2001-09-01 | 24500 |  NULL |     10 ||  1010 | 韦一笑    | 销售员    | 1006 | 2001-09-08 | 15000 |     0 |     30 |+-------+-----------+-----------+------+------------+-------+-------+--------+

找出部门编号为10中所有经理，部门编号为30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=30) or (job !='经理' and job!='销售员' and comm>=20000);+-------+-----------+-----------+------+------------+-------+-------+--------+| empno | ename     | job       | mgr  | hiredate   | sai   | comm  | deptno |+-------+-----------+-----------+------+------------+-------+-------+--------+|  1002 | 黛绮丝    | 销售员    | 1006 | 2001-02-20 | 16000 |  3000 |     30 ||  1003 | 殷天正    | 销售员    | 1006 | 2001-02-22 | 12500 |  5000 |     30 ||  1005 | 谢逊      | 销售员    | 1006 | 2001-09-28 | 12500 | 14000 |     30 ||  1007 | 张飞      | 经理      | 1009 | 2001-09-01 | 24500 |  NULL |     10 ||  1010 | 韦一笑    | 销售员    | 1006 | 2001-09-08 | 15000 |     0 |     30 ||  1015 | 张三      | 保洁员    | 1001 | 2013-05-01 | 80000 | 50000 |     50 |+-------+-----------+-----------+------+------------+-------+-------+--------+

无奖金或奖金低于1000的员工：

mysql> select * from emp where comm is null or comm<1000;+-------+-----------+-----------+------+------------+-------+------+--------+| empno | ename     | job       | mgr  | hiredate   | sai   | comm | deptno |+-------+-----------+-----------+------+------------+-------+------+--------+|  1001 | 甘宁      | 文员      | 1013 | 2000-12-17 |  8000 | NULL |     20 ||  1004 | 刘备      | 经理      | 1009 | 2001-04-02 | 29750 | NULL |     20 ||  1006 | 关羽      | 经理      | 1009 | 2001-05-01 | 28500 | NULL |     30 ||  1007 | 张飞      | 经理      | 1009 | 2001-09-01 | 24500 | NULL |     10 ||  1008 | 诸葛亮    | 分析师    | 1004 | 2007-04-19 | 30000 | NULL |     20 ||  1009 | 曾阿牛    | 董事长    | NULL | 2001-11-17 | 50000 | NULL |     10 ||  1010 | 韦一笑    | 销售员    | 1006 | 2001-09-08 | 15000 |    0 |     30 ||  1011 | 周泰      | 文员      | 1006 | 2007-05-23 | 11000 | NULL |     20 ||  1012 | 程普      | 文员      | 1006 | 2001-12-03 |  9500 | NULL |     30 ||  1013 | 庞统      | 分析师    | 1004 | 2001-12-03 | 30000 | NULL |     20 ||  1014 | 黄盖      | 文员      | 1007 | 2002-01-23 | 13000 | NULL |     10 |+-------+-----------+-----------+------+------------+-------+------+--------+

查询名字由三个字组成的员工：

mysql> select ename from emp where char_length(ename)=3;+-----------+| ename     |+-----------+| 黛绮丝    || 殷天正    || 诸葛亮    || 曾阿牛    || 韦一笑    |+-----------+

查询2000年入职的员工：

mysql> select *  from emp where year(hiredate)=2000;                     +-------+--------+--------+------+------------+------+------+--------+| empno | ename  | job    | mgr  | hiredate   | sai  | comm | deptno |+-------+--------+--------+------+------------+------+------+--------+|  1001 | 甘宁   | 文员   | 1013 | 2000-12-17 | 8000 | NULL |     20 |+-------+--------+--------+------+------------+------+------+--------+

询所有员工详细信息，用编号升序排序：

mysql> select *  from emp order by empno;+-------+-----------+-----------+------+------------+-------+-------+--------+| empno | ename     | job       | mgr  | hiredate   | sai   | comm  | deptno |+-------+-----------+-----------+------+------------+-------+-------+--------+|  1001 | 甘宁      | 文员      | 1013 | 2000-12-17 |  8000 |  NULL |     20 ||  1002 | 黛绮丝    | 销售员    | 1006 | 2001-02-20 | 16000 |  3000 |     30 ||  1003 | 殷天正    | 销售员    | 1006 | 2001-02-22 | 12500 |  5000 |     30 ||  1004 | 刘备      | 经理      | 1009 | 2001-04-02 | 29750 |  NULL |     20 ||  1005 | 谢逊      | 销售员    | 1006 | 2001-09-28 | 12500 | 14000 |     30 ||  1006 | 关羽      | 经理      | 1009 | 2001-05-01 | 28500 |  NULL |     30 ||  1007 | 张飞      | 经理      | 1009 | 2001-09-01 | 24500 |  NULL |     10 ||  1008 | 诸葛亮    | 分析师    | 1004 | 2007-04-19 | 30000 |  NULL |     20 ||  1009 | 曾阿牛    | 董事长    | NULL | 2001-11-17 | 50000 |  NULL |     10 ||  1010 | 韦一笑    | 销售员    | 1006 | 2001-09-08 | 15000 |     0 |     30 ||  1011 | 周泰      | 文员      | 1006 | 2007-05-23 | 11000 |  NULL |     20 ||  1012 | 程普      | 文员      | 1006 | 2001-12-03 |  9500 |  NULL |     30 ||  1013 | 庞统      | 分析师    | 1004 | 2001-12-03 | 30000 |  NULL |     20 ||  1014 | 黄盖      | 文员      | 1007 | 2002-01-23 | 13000 |  NULL |     10 ||  1015 | 张三      | 保洁员    | 1001 | 2013-05-01 | 80000 | 50000 |     50 |+-------+-----------+-----------+------+------------+-------+-------+--------+

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

查询每个部门的平均工资：

mysql> select deptno,avg(sai)  from emp group by deptno;+--------+------------+| deptno | avg(sai)   |+--------+------------+|     10 | 29166.6667 ||     20 | 21750.0000 ||     30 | 15666.6667 ||     50 | 80000.0000 |+--------+------------+4 rows in set (0.00 sec)

查询每个部门的雇员数量：

mysql> select deptno,count(empno)  from emp group by deptno;           +--------+--------------+| deptno | count(empno) |+--------+--------------+|     10 |            3 ||     20 |            5 ||     30 |            6 ||     50 |            1 |+--------+--------------+mysql> select deptno,count(ename)  from emp group by deptno;    +--------+--------------+| deptno | count(ename) |+--------+--------------+|     10 |            3 ||     20 |            5 ||     30 |            6 ||     50 |            1 |+--------+--------------+

查询每种工作的最高工资、最低工资、人数：

mysql> select  max(sai),min(sai) ,count(empno) from emp group by job;+----------+----------+--------------+| max(sai) | min(sai) | count(empno) |+----------+----------+--------------+|    80000 |    80000 |            1 ||    30000 |    30000 |            2 ||    13000 |     8000 |            4 ||    29750 |    24500 |            3 ||    50000 |    50000 |            1 ||    16000 |    12500 |            4 |+----------+----------+--------------+

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