在mysql中minus两张表的差集

在DB2和Oracle中，我们经常会用到minus这个函数，但是MySql中是没有minus的，那么要怎么办呢？


下面以一个小栗子来说下：
```

mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t_eg_01 |
| t_eg_02 |
+----------------+
2 rows in set (0.00 sec)

mysql> desc t_eg_01;
+--------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+--------------+------+-----+---------+-------+
| id | varchar(5) | NO | PRI | NULL | |
| name | varchar(20) | YES | | NULL | |
| remark | varchar(255) | YES | | NULL | |
+--------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

mysql> desc t_eg_02;
+--------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+--------------+------+-----+---------+-------+
| id | varchar(5) | NO | PRI | NULL | |
| name | varchar(20) | YES | | NULL | |
| remark | varchar(255) | YES | | NULL | |
+--------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

数据信息

mysql> select * from t_eg_01 \G
*************************** 1. row ***************************
id: 1
name: 张三
remark: 特长：音乐
*************************** 2. row ***************************
id: 2
name: 李四
remark: 爱好：游泳
*************************** 3. row ***************************
id: 3
name: 王五
remark: 富二代
3 rows in set (0.00 sec)

mysql> select * from t_eg_02 \G
*************************** 1. row ***************************
id: 1
name: 张三
remark: 特长：音乐
*************************** 2. row ***************************
id: 3
name: 王五
remark: 富二代
*************************** 3. row ***************************
id: 5
name: 光头
remark: 平民
3 rows in set (0.00 sec)

如果用minus会直接报错

通过left join实现minus的效果，如下图所示，应该得到id为2的数据
```
```
mysql> select a.* from t_eg_01 a
-> left join
-> t_eg_02 b
-> on a.id=b.id
-> where b.id is null;
+----+--------+-----------------+
| id | name | remark |
+----+--------+-----------------+
| 2 | 李四 | 爱好：游泳 |
+----+--------+-----------------+
1 row in set (0.00 sec)
```