Question

我有2张桌子（下面的样本）

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 相等且dateout null

的数据

我正在使用下面的查询，但我得到空的回复。

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

我缺少什么意思？

Answer 1

您需要在查询中添加EXISTS：

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，没有为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)

Answer 2

试试这个

  SELECT name,datein,dateout FROM(select * from atable union select * from btable)as tt 
where tt.name ='test' and tt.dateout is null;

MySQL＆＃34; AND＆＃34;声明问题

2 个答案: