将三个类似的sql查询合并为一个结果

Question

我有一张桌子说（TimeValue）像这样

 Time    Value   Owner
 ======================
 1      10       A
 2      20       B
 3      30       C
 4      40       A
 5      50       B
 6      60       C
 7      70       A
 8      80       B

现在我有三个sql语句，如下所示

1. select owner, value as 'First sql' from TimeValue where time >= 1 and time <= 3 group by owner

2. select owner, value as 'Second sql' from TimeValue where time >= 4 and time <= 6 group by owner

3. select owner, value as 'Third sql' from TimeValue where time >= 7 and time <= 9 group by owner

现在这些是上面的sql的结果

1。

Value   Owner
=================
10       A
20       B
30       C

2。

Value   Owner
=================
40       A
50       B
60       C

3

Value   Owner
===============
70       A
80       B
90       C

我的问题是，如果我想要以下结果，sql语句将是什么？

 Owner    First SQL     Second SQL     Third SQL
==================================================
  A        10            40              70
  B        20            50              80
  C        30            60              90

先感谢您

Answer 1

一种方法是使用CASE语句，如下所示：

SELECT
    owner
,   MAX(CASE WHEN time >= 1 AND time <= 3 THEN value ELSE NULL END) AS FIRST
,   MAX(CASE WHEN time >= 4 AND time <= 6 THEN value ELSE NULL END) AS SECOND
,   MAX(CASE WHEN time >= 7 AND time <= 9 THEN value ELSE NULL END) AS THIRD
FROM TimeValue
GROUP BY owner

请注意，您需要在value周围添加一个汇总函数，例如MAX 。 实际上，如果没有RDBMS引擎的聚合功能，许多引擎甚至都不会采用SQL。

Answer 2

SQL字段

select owner, 
SUM(case when (time >= 1 and time <= 3) then value end) as 'FirstSQL',
SUM(case when (time >= 4 and time <= 6) then value end) as 'SecondSQL',
SUM(case when (time >= 7 and time <= 9) then value end) as 'ThirdSQL'
from TimeValue 
group by owner

根据您的示例，您应该使用SUM而不是MAX

Answer 3

dasblinkenlight的想法相同，但方法不同，我同意汇总功能，例如MAX或SUM

SELECT
    owner,
MAX(IF(time between 1 and 3, value,NULL) ) as first,
MAX(IF(time between 4 and 6, value,NULL) ) as sec,
MAX(IF(time between 7 and 9, value,NULL) ) as third

FROM TimeValue 
GROUP BY owner

Answer 4

您还可以使用自我联接：

select
  tv0.owner
, tv0.value sql1
, tv1.value sql2
, tv2.value sql3

from timevalue tv0
inner join timevalue tv1 on tv1.owner = tv0.owner
inner join timevalue tv2 on tv2.owner = tv0.owner

where tv0.time between 1 and 3
and tv1.time between 4 and 6
and tv2.time between 7 and 9