Question

I have 3 queries. If the first one returns empty set, I execute the second query, and if it returns empty set too, I give to the server the last chance and do the third:

SELECT ... INTO #Query1
IF EXISTS(SELECT * FROM #Query1)
    SELECT * FROM #Query1
ELSE BEGIN
    SELECT ... INTO #Query2
IF EXISTS(SELECT * FROM #Query2)
    SELECT * FROM #Query2
ELSE BEGIN
    SELECT ...
    END
END

It worked well, but I’ve faced a new task – the query should be used as a subquery as well as other queries, within IF EXISTS([subquery]). Doing this, I see

Incorrect syntax near the keyword ‘INTO’.

How should I modify the original query to meet this new condition?

Regards,

Answer 1

Are you looking for something like this:

create function dbo.Foo()
  returns @Result table ( ThingId Int, Source Int )
as
begin
  insert into @Result
    select ThingId, 1 as Source from Things1
  if @@ROWCOUNT = 0
    insert into @Result
      select ThingId, 2 as Source from Things2
  if @@ROWCOUNT = 0
    insert into @Result
      select ThingId, 3 as Source from Things3
  --...
  return
end
go
select * from dbo.Foo()
select 42 as 'The Answer' where exists ( select * from dbo.Foo() where Source > 9 )

You can pass parameters into the function to use in WHERE clauses and the like. The Source column may be omitted if you don’t care to know where the data originated.