Question

我有一张关联表。行看起来像：id, objectID, thingID。

我需要一个存储过程来执行一个返回3个值的select语句：

item1ID, item2ID, item3ID

所以查询看起来像：

SELECT TOP 3 objectID WHERE thingID = 7 -- (or something)

但是，可能并不总是返回三行。

存储过程看起来像行返回行的值是什么，但如果没有返回3，则剩下的行为零？

的示例：

数据

id：1，objectID：12，thingID：2
id：2，objectID：13，thingID：2
id：3，objectID：14，thingID：3
id：4，objectID：15，thingID：3
id：5，objectID：16，thingID：3

结果，其中thingID = 2

item1ID: 12, item2ID: 13, item3ID: 0

结果，其中thingID = 3

item1ID: 14, item2ID: 15, item3ID: 16

Answer 1

与其他答案类似，但使用sql表变量而不是临时表当proc完成时，SQL表变量被清除。

create proc ReturnTop3
as
begin

    declare @returnTable as table (
        objectId int
    )

    declare @count int


    insert into @returnTable
        SELECT TOP 3 objectID WHERE thingID = 7

    set @count = (select COUNT(*) from @returnTable)

    while (@count < 3)
        begin
            insert into @returnTable select 0
            select @count = @count + 1
        end

    select * from @returnTable
end

Answer 2

您可以创建临时表并以此方式执行

    Create table #test (Id int);

    INSERT INTO #test
    SELECT TOP 3 objectID WHERE thingID = 7



    WHILE (SELECT COUNT(1) from #test) < 3
    BEGIN
        INSERT INTO #test 
        VALUES (0)
    END

    SELECT * FROM #test

    DROP TABLE #test

Answer 3

你可以做这样的事情看小提琴

http://sqlfiddle.com/#!3/ed8ca/10

select TOP 3 ID, thing
from
(
select 0 as srt,ID,thing from tbl
where thing = 2
union all
select 1 as srt,0 as ID, 0 as thing
union all
select 2 as srt,0 as ID, 0 as thing
union all
select 3 as srt,0 as ID, 0 as thing
) as t
order by srt,thing

Answer 4

这样的东西？

DECLARE @InputThingID INT = 2

DECLARE @ID AS INT, @ItemID1 AS INT = 0, @ItemID2 AS INT = 0, @ItemID3 AS Int = 0
SELECT * INTO #Temp FROM MyTable WHERE ThingID=@InputThingID
SELECT TOP 1 @ID=ID, @ItemID1 = ObjectID FROM #Temp
DELETE FROM #Temp WHERE ID=@ID
SELECT TOP 1 @ID=ID, @ItemID2 = ObjectID FROM #Temp
DELETE FROM #Temp WHERE ID=@ID
SELECT TOP 1 @ID=ID, @ItemID3 = ObjectID FROM #Temp
DELETE FROM #Temp WHERE ID=@ID
SELECT @ItemID1 AS ItemID1, @ItemID2 AS ItemID2, @ItemID3 AS ItemID3
DROP TABLE #Temp

Answer 5

这可能是最好的，也是最普遍的，但可能也是最困难的解决方案。需要聚合MAX函数，但不影响结果。

SELECT [1] AS Item1ID,[2] AS Item2ID, [3] AS Item3ID FROM
    (SELECT ROW_NUMBER() 
     OVER(order by id) rownum,objectId FROM data where thingId = 3) AS rows
    PIVOT(
    MAX(objectId)
    FOR rownum IN ([1],[2],[3])
    ) as piv

如何在此存储过程中始终返回3个值？

5 个答案: