MySQL "AND"语句问题

Question

我有 2 个表(下面的示例)

aTable
-------------------------------------------------
name    |   datein                  |   dateout
test    |   2016-10-10 00:00:00     |   null --->> This one
test2   |   2016-10-12 00:00:00     |   null
-------------------------------------------------

bTable
------------------------------------------------------------
name    |   datein                  |   dateout
test    |   2016-05-05 00:00:00     |   2016-06-06 00:00:00 
test    |   2016-10-10 00:00:00     |   null --->> This one
test2   |   2016-10-12 00:00:00     |   2016-10-13 00:00:00
------------------------------------------------------------

我想提取name、datein equal 和dateout 都为 的数据空

我正在使用下面的查询，但得到的响应是空的。

SELECT name,datein 
FROM aTable 
WHERE (name = 'test' AND dateout IS NULL) AND 
      (SELECT name FROM bTable WHERE name = 'test' AND dateout IS NULL)

我有什么遗漏的地方吗？

Answer 1

您需要将 EXISTS 添加到您的查询中:

SELECT t1.name, t1.datein 
FROM aTable AS t1
WHERE (t1.name = 'test' AND t1.dateout IS NULL) AND 
      EXISTS(SELECT name 
             FROM bTable AS t2
             WHERE t2.name = 'test' AND 
                   t2.datein = t1.datein AND
                   t2.dateout IS NULL)

或者，不为 name 字段提供特定值:

SELECT t1.name, t1.datein 
FROM aTable AS t1
WHERE t1.dateout IS NULL AND 
      EXISTS(SELECT name 
             FROM bTable AS t2
             WHERE t2.name = t1.name AND 
                   t2.datein = t1.datein AND
                   t2.dateout IS NULL)