Question

我目前在存储过程中有以下代码（见下文）。为了总共获得10个结果，我拿下了每个联盟的前五名。但是，我想取UNION的前10名，而不是每个中的5名。有任何想法吗？这可能吗？

BEGIN
SELECT TOP 5
    a_object_ID as [id], 
    a_object_name as [name],
    'A_object' as [Type]
FROM [database].[dbo].[table_a]
WHERE a_object_name LIKE @Search + '%'

UNION ALL

SELECT TOP 5 
    b_object_ID as [id], 
    b_object_name as [name],
    'B_object' as [Type]
FROM [database].[dbo].[table_b]
WHERE b_object_name LIKE @Search + '%'

ORDER BY [name]
END

Answer 1

是的，非常可能。您只需从联合结果中选择前10名。

SELECT TOP 10 * FROM (
    SELECT
        a_object_ID as [id], 
        a_object_name as [name],
        'A_object' as [Type]
    FROM [database].[dbo].[table_a]
    WHERE a_object_name LIKE @Search + '%'

    UNION ALL

    SELECT
        b_object_ID as [id], 
        b_object_name as [name],
        'B_object' as [Type]
    FROM [database].[dbo].[table_b]
    WHERE b_object_name LIKE @Search + '%'
) u
ORDER BY u.[name]

Answer 2

使您的UNION成为子查询

SELECT TOP 10 * 
FROM (
  SELECT
      a_object_ID as [id], 
      a_object_name as [name],
      'A_object' as [Type]
  FROM [database].[dbo].[table_a]
  WHERE a_object_name LIKE @Search + '%'

  UNION ALL

  SELECT
      b_object_ID as [id], 
      b_object_name as [name],
      'B_object' as [Type]
  FROM [database].[dbo].[table_b]
  WHERE b_object_name LIKE @Search + '%'
) AS subquery
ORDER BY subquery.[name]

Answer 3

这个怎么样？

SELECT TOP 10 *
FROM
(
SELECT a_object_ID as [id], 
    a_object_name as [name],
    'A_object' as [Type]
FROM [database].[dbo].[table_a]
WHERE a_object_name LIKE @Search + '%'
UNION ALL
SELECT b_object_ID as [id], 
    b_object_name as [name],
    'B_object' as [Type]
FROM [database].[dbo].[table_b]
WHERE b_object_name LIKE @Search + '%'
) x
ORDER BY [name]

Answer 4

为什么要使查询复杂化？这将完成这项工作：

set rowcount 10

  SELECT a_object_ID as [id], 
         a_object_name as [name],
         'A_object' as [Type]
  FROM [database].[dbo].[table_a]
  WHERE a_object_name LIKE @Search + '%'
UNION ALL
  SELECT b_object_ID as [id], 
         b_object_name as [name],
         'B_object' as [Type]
  FROM [database].[dbo].[table_b]
  WHERE b_object_name LIKE @Search + '%'
ORDER BY [name]

set rowcount 0

Answer 5

上述答案是浪费的，因为子查询收集然后拒绝可能大量的行。您可以使用子查询改进问题。

declare @Recs int = 10;

with cte1 as (
SELECT TOP (@Recs)
    a_object_ID as [id], 
    a_object_name as [name],
    'A_object' as [Type]
FROM [database].[dbo].[table_a]
WHERE a_object_name LIKE @Search + '%'
)
, cte2 as
(
SELECT TOP (@Recs)
    a_object_ID as [id], 
    a_object_name as [name],
    'B_object' as [Type]
FROM [database].[dbo].[table_a]
WHERE a_object_name LIKE @Search + '%'
)
SELECT TOP (@Recs) [id], [name], [Type]
(
select [id], [name], [Type] from cte1
union all
select [id], [name], [Type] from cte2
) SQ
ORDER BY [Name]

如何在sql中获取UNION的前10个结果？

5 个答案: