Question

我想在my_table上使用查询中的id来从my_table_2中选择所有field_b行。

  SELECT field_b
  FROM my_table_2
  WHERE my_id_2 IN (
         SELECT my_id FROM my_table WHERE field_a = 1234
  );

我让ERROR 1054 (42S22): Unknown column 'my_id_2' in 'IN/ALL/ANY subquery'执行上述查询。

以下是我的表格示例供参考：

  mysql> select * from my_table;
    +-------+---------+
    | my_id | field_a |
    +-------+---------+
    |     1 |    1234 |
    +-------+---------+
    |     2 |    1234 |
    +-------+---------+
    2 row in set (0.00 sec)

mysql> select * from my_table_2;
+-------+-----------+
| my_id_2 | field_b |
+---------+---------+
|     1   |  5678   |
+-------+-----------+
1 row in set (0.00 sec)

Answer 1

另一种方式

SELECT field_b
FROM my_table_2 m2
WHERE EXISTS (
     SELECT my_id FROM my_table 
     WHERE field_a = 1234 and m2.my_id_2=my_table.my_id
);

Answer 2

该查询可以重写为简单的连接操作：

SELECT field_b
FROM my_table_2
INNER JOIN my_table ON my_table_2.my_id_2 = my_table.my_id
WHERE field_a = 1234;

MySQL子查询IN结果

2 个答案: