SQL Server：加入2个查询，性能问题

Question

I have two (rather complex) functions which both return a table;

(SELECT Id, x, y FROM fnGetXY(3)) (execution takes +/- 5 sec)

(SELECT Id, a, b FROM fnGetAB(3)) (execution takes +/- 15 sec)

I want to combine the result;

SELECT X.Id, x, y, a, b FROM 
(
 (SELECT Id, x, y FROM fnGetXY(3)) X
 JOIN (SELECT Id, a, b FROM fnGetAB(3)) Y ON X.Id=Y.Id
)

The result is correct, however this does not take the expected +/- 20-25 seconds, but 90 seconds.

Is there any way I can force a combination of the results of the two queries in a way that consumes maximum slightly more than the sum of each?

[Update]

1. #temp; As this is part of a function, a #temp table is not an option unfortunately.
2. I have tried LEFT JOIN instead of JOIN with no result, but it appears that FULL OUTER JOIN solves this case..

Thanks everybody!

Answer 1

In most cases the solution is to save the intermediate results into #temp tables and then join the results:

select Id, x, y
into #t1
from fnGetXY(3)

select Id, a, b 
into #t2
from fnGetAB(3)

SELECT #t1.Id, x, y, a, b 
FROM #t1
INNER JOIN #t2 on #t1.id = #t2.id

SQL Server optimizer doesn't like dealing with functions very much (except the inline TVFs).

Answer 2

You should be able to JOIN these two functions as you would join two table, I think these sub-queries are just an overkill of a fairly simple query. Try something like ....

SELECT t1.Id
     , t1.x
     , t1.y
     , t2.a 
     , t2.b 
FROM fnGetXY(3) t1 INNER JOIN fnGetAB(3) t2
ON t1.Id = t2.Id