Question

我有两个像这样的结构表：

表a

id title   date
1  testing1 2001-05
1  testing2 2003-05

表格b

id code   date
1  aaaa 2001-01
1  bbbb 2003-01

当我加入这两个表时，我得到三行，但我只想要2？

(query)
select distinct a.*, b.*
from table a, table b
where a.date in ('2001-05','2003-05')
and a.id=b.id
and b.date < a.date  ---> I know the error is coming from here.

错误的输出看起来像这样

id title   date     id   code   date
1  testing1 2001-05 1    aaaa   2001-01
1  testing1 2003-05 1    aaaa   2003-01-------this is duplicated because the date is in fact less than, 
1  testing2 2003-05 1    bbbb   2003-01

正确的输出应该是：

id title   date     id   code   date
1  testing1 2001-05 1    aaaa   2001-01
1  testing2 2003-05 1    bbbb   2003-01

Answer 1

您可能希望ID：s是唯一的。将主键添加到ID列。

Answer 2

Select A.id, A.title, A.date
    , B.id, B.code, B.date
From TableA As A
    Join    (
            Select A.id, A.title, A.date
                , Min( B.Date ) As BDate
            From TableA As A
                Left Join TableB As B
                    On B.id = A.id
                        And B.Date < A.Date
            Where A.Date In('2001-05-01','2003-05-01')
            Group By A.id, A.title, A.date
            ) As Z
        On Z.id = A.id
            And Z.title = A.title
            And Z.date = A.date
    Join TableB As B
        On B.id = A.id
            And B.date = Z.BDate

需要SQL查询的帮助

2 个答案: