How to work around SQL Server's “The maximum number of tables in a query (260) was exceeded.”

Question

i have a query that contains a series of 21 UNIONs, e.g.:

CREATE VIEW dbo.USGovCurrencyOnHandBreakdown AS

   SELECT ... FROM a
   UNION ALL
   SELE         


        

Answer 1

You could store the subqueries into temp tables, e.g. the USGovCurrencyOnHandBreakdown_Additions and USGovCurrencyOnHandBreakdown_Subtractions that you mentioned, and than selecting from those temp tables instead of views.

Of course, the transactions could be an issue because of the dirty reads, I don't know if that's a concern in this case...

Answer 2

A colleague came up with a great answer. Use a function to return a table variable; insert the results into the table variable bit by bit:

CREATE VIEW dbo.USGovCurrencyOnHandBreakdown AS
    SELECT * FROM fn_USGovCurrencyOnHandBreakdown()

with the view now calling the UDF:

CREATE FUNCTION dbo.fn_USGovCurrencyOnHandBreakdown()
    RETURNS @Results TABLE
    (
        Total money, 
        ...
    )

    INSERT INTO @Results SELECT ... FROM a
    INSERT INTO @Results SELECT ... FROM b
    INSERT INTO @Results SELECT ... FROM c
    INSERT INTO @Results SELECT ... FROM d
      ...
    INSERT INTO @Results SELECT ... FROM u

    RETURN 
END

As far as any clients know the view is unchanged. (Except now it works!)