MySQL 如何在两个表之间找到缺失值

要在两个MySQL表之间找到缺失值，可以使用NOT IN。让我们首先创建一个表 –

mysql> create table DemoTable1(Value int);
Query OK, 0 rows affected (0.56 sec)

使用插入命令在表中插入一些记录 –

mysql> insert into DemoTable1 values(1);
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable1 values(2);
Query OK, 1 row affected (0.28 sec)
mysql> insert into DemoTable1 values(5);
Query OK, 1 row affected (0.23 sec)
mysql> insert into DemoTable1 values(6);
Query OK, 1 row affected (0.09 sec)
mysql> insert into DemoTable1 values(8);
Query OK, 1 row affected (0.16 sec)

使用select语句显示表中的所有记录 –

mysql> select *from DemoTable1;

这将产生以下输出 –

+-------+
| Value |
+-------+
|     1 |
|     2 |
|     5 |
|     6 |
|     8 |
+-------+
5 rows in set (0.00 sec)

以下是创建第二个表的查询 –

mysql> create table DemoTable2(Value int);
Query OK, 0 rows affected (1.19 sec)

使用插入命令在表中插入一些记录 –

mysql> insert into DemoTable2 values(1);
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable2 values(2);
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable2 values(3);
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable2 values(4);
Query OK, 1 row affected (0.12 sec)

使用select语句显示表中的所有记录 –

mysql> select *from DemoTable2;

这将产生以下输出 –

+-------+
| Value |
+-------+
|     1 |
|     2 |
|     3 |
|     4 |
+-------+
4 rows in set (0.00 sec)

以下是在两个MySQL表之间查找缺失值的查询 –

mysql> select Value from DemoTable1 where Value not in(select Value from DemoTable2);

这将产生以下输出 –

+-------+
| Value |
+-------+
|     5 |
|     6 |
|     8 |
+-------+
3 rows in set (0.07 sec)

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