数据库第二次作业

1.创建表

mysql>  create table t_worker(
    ->     department_id int(11) not null comment '部门号',
    ->     worker_id int(11) primary key not null comment '职工号',
    ->     worker_date date not null comment '工作时间',
    ->     wages float(8,2) not null comment '工资',
    ->     politics varchar(10) not null default '群众' comment '政治面貌',
    ->     name varchar(20) not null comment '姓名',
    ->     borth_date date not null comment '出生日期' );
Query OK, 0 rows affected, 3 warnings (0.02 sec)

mysql> desc t_worker;
+---------------+-------------+------+-----+---------+-------+
| Field         | Type        | Null | Key | Default | Extra |
+---------------+-------------+------+-----+---------+-------+
| department_id | int         | NO   |     | NULL    |       |
| worker_id     | int         | NO   | PRI | NULL    |       |
| worker_date   | date        | NO   |     | NULL    |       |
| wages         | float(8,2)  | NO   |     | NULL    |       |
| politics      | varchar(10) | NO   |     | 群众    |       |
| name          | varchar(20) | NO   |     | NULL    |       |
| borth_date    | date        | NO   |     | NULL    |       |
+---------------+-------------+------+-----+---------+-------+
7 rows in set (0.01 sec)

2.插入数据

insert into t_worker values (101,1001,'2015-5-4',7500.00,'群众','张春燕','1990-7-1');
insert into t_worker values (101,1002,'2019-2-6',5200.00,'团员','李名博','1997-2--8');
insert into t_worker values (102,1003,'2008-1-4',10500.00,'党员','王博涵','1983-6-8');
insert into t_worker values (102,1004,'2016-10-10',5500.00,'群众','赵小军','1994-9-5');
insert into t_worker values (102,1005,'2014-4-1',8800.00,'党员','钱有财','1992-12-30');
insert into t_worker values (103,1006,'2019-5-5',5500.00,'党员','孙菲菲','1996-9-2');

3. 完成查询

（1）、显示所有职工的基本信息。

mysql> select * from t_worker;
+---------------+-----------+-------------+----------+----------+--------+------------+
| department_id | worker_id | worker_date | wages    | politics | name   | borth_date |
+---------------+-----------+-------------+----------+----------+--------+------------+
|           101 |      1001 | 2015-05-04  |  7500.00 | 群众     | 张春燕 | 1990-07-01 |
|           101 |      1002 | 2019-02-06  |  5200.00 | 团员     | 李名博 | 1997-02-08 |
|           102 |      1003 | 2008-01-04  | 10500.00 | 党员     | 王博涵 | 1983-06-08 |
|           102 |      1004 | 2016-10-10  |  5500.00 | 群众     | 赵小军 | 1994-09-05 |
|           102 |      1005 | 2014-04-01  |  8800.00 | 党员     | 钱有财 | 1992-12-30 |
|           103 |      1006 | 2019-05-05  |  5500.00 | 党员     | 孙菲菲 | 1996-09-02 |
+---------------+-----------+-------------+----------+----------+--------+------------+
6 rows in set (0.01 sec)

mysql>

（2）、查询所有职工所属部门的部门号，不显示重复的部门号。

# 去重查询
select distinct 字段列表 from 表名;    # 使重复的数据只显示一条

# 在对字段进行去重的时候，要保证distinct在所有字段的最前面
# 如果distinct关键字后面有多个字段时，则会对多个字段进行组合去重，只有多个字段组合起来的值是相等的才会被去重

mysql> SELECT DISTINCT department_id FROM t_worker;
+---------------+
| department_id |
+---------------+
|           101 |
|           102 |
|           103 |
+---------------+
3 rows in set (0.00 sec)

mysql>

（3）求出所有职工的人数。

mysql> SELECT COUNT(*) AS total_workers FROM t_worker;
+---------------+
| total_workers |
+---------------+
|             6 |
+---------------+
1 row in set (0.01 sec)

mysql>

（4）、列出最高工和最低工资。

mysql> SELECT MAX(wages) AS max_wage, MIN(wages) AS min_wage FROM t_worker;
+----------+----------+
| max_wage | min_wage |
+----------+----------+
| 10500.00 |  5200.00 |
+----------+----------+
1 row in set (0.00 sec)

mysql>

（5）、列出职工的平均工资和总工资。

mysql> SELECT AVG(wages) AS avg_wage, SUM(wages) AS total_wage FROM t_worker;
+-------------+------------+
| avg_wage    | total_wage |
+-------------+------------+
| 7166.666667 |   43000.00 |
+-------------+------------+
1 row in set (0.00 sec)

mysql>

（6）、创建一个只有职工工号、姓名和参加工作的新表，名为工作日期表。

mysql> CREATE TABLE work_date_table AS SELECT worker_id, name, worker_date FROM t_worker;
Query OK, 6 rows affected (0.03 sec)
Records: 6  Duplicates: 0  Warnings: 0

mysql> select * from work_date_table;
+-----------+--------+-------------+
| worker_id | name   | worker_date |
+-----------+--------+-------------+
|      1001 | 张春燕 | 2015-05-04  |
|      1002 | 李名博 | 2019-02-06  |
|      1003 | 王博涵 | 2008-01-04  |
|      1004 | 赵小军 | 2016-10-10  |
|      1005 | 钱有财 | 2014-04-01  |
|      1006 | 孙菲菲 | 2019-05-05  |
+-----------+--------+-------------+
6 rows in set (0.00 sec)

mysql>

（7）、显示所有党员的年龄。

mysql> SELECT name, TIMESTAMPDIFF(YEAR, borth_date, CURDATE()) AS age FROM t_worker WHERE politics = '党员';
+--------+------+
| name   | age  |
+--------+------+
| 王博涵 |   42 |
| 钱有财 |   32 |
| 孙菲菲 |   28 |
+--------+------+
3 rows in set (0.00 sec)

或 表达式显示

（8）、列出工资在4000---8000之间的所有职工姓名。

mysql> SELECT name FROM t_worker WHERE wages BETWEEN 4000 AND 8000;
+--------+
| name   |
+--------+
| 张春燕 |
| 李名博 |
| 赵小军 |
| 孙菲菲 |
+--------+
4 rows in set (0.00 sec)

（9）、列出所有孙姓和李姓的职工姓名。

mysql> SELECT name FROM t_worker WHERE name LIKE '孙%' OR name LIKE '李%';
+--------+
| name   |
+--------+
| 李名博 |
| 孙菲菲 |
+--------+
2 rows in set (0.00 sec)

（10）、列出所有部门号为102和103且不是党员的职工号、姓名。

mysql> SELECT worker_id, name FROM t_worker WHERE department_id IN (102,103) AND politics != '党员';
+-----------+--------+
| worker_id | name   |
+-----------+--------+
|      1004 | 赵小军 |
+-----------+--------+
1 row in set (0.00 sec)

（11）、将职工表t_worker中的职工按出生的先后顺序排序。

mysql> SELECT * FROM t_worker ORDER BY borth_date;
+---------------+-----------+-------------+----------+----------+--------+------------+
| department_id | worker_id | worker_date | wages    | politics | name   | borth_date |
+---------------+-----------+-------------+----------+----------+--------+------------+
|           102 |      1003 | 2008-01-04  | 10500.00 | 党员     | 王博涵 | 1983-06-08 |
|           101 |      1001 | 2015-05-04  |  7500.00 | 群众     | 张春燕 | 1990-07-01 |
|           102 |      1005 | 2014-04-01  |  8800.00 | 党员     | 钱有财 | 1992-12-30 |
|           102 |      1004 | 2016-10-10  |  5500.00 | 群众     | 赵小军 | 1994-09-05 |
|           103 |      1006 | 2019-05-05  |  5500.00 | 党员     | 孙菲菲 | 1996-09-02 |
|           101 |      1002 | 2019-02-06  |  5200.00 | 团员     | 李名博 | 1997-02-08 |
+---------------+-----------+-------------+----------+----------+--------+------------+
6 rows in set (0.00 sec)

（12）、显示工资最高的前3名职工的职工号和姓名。

mysql> SELECT worker_id, name FROM t_worker ORDER BY wages DESC LIMIT 3;
+-----------+--------+
| worker_id | name   |
+-----------+--------+
|      1003 | 王博涵 |
|      1005 | 钱有财 |
|      1001 | 张春燕 |
+-----------+--------+
3 rows in set (0.00 sec)

（13）、求出各部门党员的人数。

> SELECT department_id, COUNT(*) AS party_members
    -> FROM t_worker
    -> WHERE politics = '党员'
    -> GROUP BY department_id;
+---------------+---------------+
| department_id | party_members |
+---------------+---------------+
|           102 |             2 |
|           103 |             1 |
+---------------+---------------+
2 rows in set (0.00 sec)

（14）、统计各部门的工资和平均工资并保留2位小数

mysql> SELECT department_id,
    ->        ROUND(SUM(wages), 2) AS total_wages,
    ->        ROUND(AVG(wages), 2) AS avg_wages
    -> FROM t_worker
    -> GROUP BY department_id;
+---------------+-------------+-----------+
| department_id | total_wages | avg_wages |
+---------------+-------------+-----------+
|           101 |       12700 |      6350 |
|           102 |       24800 |   8266.67 |
|           103 |        5500 |      5500 |
+---------------+-------------+-----------+
3 rows in set (0.00 sec)

（15）、列出总人数大于等于3的部门号和总人数。

mysql> SELECT department_id, COUNT(*) AS total_workers
    -> FROM t_worker
    -> GROUP BY department_id
    -> HAVING total_workers >= 3;
+---------------+---------------+
| department_id | total_workers |
+---------------+---------------+
|           102 |             3 |
+---------------+---------------+
1 row in set (0.00 sec)

mysql>