Question

我有一个SQL函数，它返回一个团队列表。

我想使用union将其他列表加入到该列表中，但前提是第一次选择返回多行。

类似的东西：

CREATE FUNCTION Teams()
RETURNS TABLE
AS
RETURN
(
  SELECT * FROM TABLE1
  if @@rowcount>1      
  UNION 
  SELECT * FROM TABLE2
  end if
)

Answer 1

不漂亮，但这应该有效：

CREATE FUNCTION Teams() 
RETURNS TABLE 
AS 
RETURN 
( 
  SELECT * FROM TABLE1 
  UNION  
  SELECT * FROM TABLE2 WHERE EXISTS (SELECT * FROM TABLE1)
 )

如果第一个表中的选择很复杂，您可以将它放入CTE：

CREATE FUNCTION Teams() 
RETURNS TABLE 
AS 
RETURN 
( 
  WITH Result AS
  (
      SELECT * FROM TABLE1 WHERE ComplicatedConditions = 1
  )
  SELECT * FROM Result
  UNION  
  SELECT * FROM TABLE2 WHERE EXISTS (SELECT * FROM Result)
 )

Answer 2

如果我理解正确

CREATE FUNCTION Teams()
RETURNS TABLE
AS
RETURN
( 
  if (select COUNT(*) from TABLE2)>1  
   SELECT * FROM TABLE1
   UNION 
   SELECT * FROM TABLE2
  else
   SELECT * FROM TABLE1
 )

Answer 3

一种方法是：

IF EXISTS(SELECT 1 FROM TABLE1)
    SELECT * FROM TABLE1
    UNION 
    SELECT * FROM TABLE2
ELSE
    SELECT * FROM TABLE1

rowcount上的sql条件联合

3 个答案: