You can return a single table from a T-SQL Function in SQL Server 2008.
I am wondering if it is possible to return more than one table.
The scenario is that I have three queries that filter 3 different tables. Each table is filtered against 5 filter tables that I would like to return from a function; rather than copy and paste their creation in each query.
An simplified example of what this would look like with copy and paste:
FUNCTION GetValuesA(@SomeParameter int) RETURNS @ids TABLE (ID int) AS
WITH Filter1 As ( Select id FROM FilterTable1 WHERE Attribute=SomeParameter )
, Filter2 As ( Select id FROM FilterTable2 WHERE Attribute=SomeParameter )
INSERT INTO @IDs
SELECT ID FROM ValueTableA
WHERE ColA IN (SELECT id FROM Filter1)
AND ColB IN (SELECT id FROM Filter2)
RETURN
-----------------------------------------------------------------------------
FUNCTION GetValuesB(@SomeParameter int) RETURNS @ids TABLE (ID int) AS
WITH Filter1 As ( Select id FROM FilterTable1 WHERE Attribute=SomeParameter )
, Filter2 As ( Select id FROM FilterTable2 WHERE Attribute=SomeParameter )
INSERT INTO @IDs
SELECT ID FROM ValueTableB
WHERE ColA IN (SELECT id FROM Filter1)
AND ColB IN (SELECT id FROM Filter2)
AND ColC IN (SELECT id FROM Filter2)
RETURNSo, the only difference between the two queries is the Table being filtered, and HOW (the Where clause).
I would like to know if I could return Filter1 & Filter2 from a function. I am also open to suggestions on different ways to approach this problem.
2条答案
按热度按时间cbeh67ev1#
No.
Conceptually, how would you expect to handle a function that returned a variable number of tables? You would
JOINon two tables at once? What if the returned fields don't line up?Is there some reason you can't have a TVF for each filter?
cigdeys32#
As others say, NO. A function in TSQL must return exactly one result (although that result can come in the form of a table with numerous values).
There are a couple of ways you could achieve something similar though. A stored procedure can execute multiple select statements and deliver the results up to whatever called it, whether that be an application layer or something like SSMS. Many libraries require you to add additional commands to access more result sets though. For instance, in Pyodbc to access result sets after the first one you need to call
cursor.nextset()Also, inside a function you could UNION several result sets together although that would require each result set to have the same columns. One way to achieve that if they have a different column structure is to add in nulls for the missing columns for each select statement. If you needed to know which select statement returned the value, you could also add a column which indicated that. This should work with your simplified example since in each case it is just returning a single ID column, but it could get awkward very quickly if the column names or types are radically different.