Covering indexes in joins
-
Hi Guys,
I have a question about using covering indexes within joins. If I use 1 column in a covering index and use it in a joins, I get a scan within my query plan.
Should I include all the columns in my joins that reference the covering index? The index has 3 columns but no 'includes' columns.
Regards
IC
-
What kind of scan - table scan, clustered index scan, or non clustered index scan? Please post the actual execution plan.
John
-
Further on John's reply, we need the table structures, the query and the actual execution plan, without the information it's only wild guesses.
-
Don't worry....I already figured it out.
Its a clustered index scan and when I include both indexes in the joins it returns a Seek instead of a Scan.
-
Imke Cronje (7/18/2016)
Don't worry....I already figured it out.Its a clustered index scan and when I include both indexes in the joins it returns a Seek instead of a Scan.
Now all you have to worry about is how many times it does the seek. Seriously. See the properties window on the icon.
As a bit of a sidebar, a seek on the execution plan is not always better than a scan, especially if a seek is done once for each row.
--Jeff Moden
RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.Change is inevitable... Change for the better is not.
Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)
Viewing 5 posts - 1 through 4 (of 4 total)
You must be logged in to reply to this topic. Login to reply