Question: In the Crystal Reports report creation wizard there is the option of changing the order which more than two two tables are linked. The link between Table A and Table B could be made before Table C is linked, or vice versa. It says "The order may affect the resulting data set." How could that be true? I could see it affecting performance but 3 linked tables should always return the same dataset, shouldn't they?
+2
A:
Depends on what type of Join crystal is using when "linking". Left and right joins will only pull matching data from either side of the "link". Any null or empty data will be discarded and in some cases you don't want that.
MkUltra
2009-12-23 20:20:43
A:
I haven't used Crystal report so far. But your underlying question is about query performance I can comment on it. What database, version you have? In Oracle 10g the rule based optimizer is replaced with cost based optimizer. RBO takes the order of tables into consideration. CBO does not. So, it should work just perfect for you.
Guru
2009-12-23 20:22:14