Re: Problem with left join when moving a column to another table

Jason Long-2 wrote
> Does the syntax you showed me have performance benefits vs joining a
> bunch of views together?

As a general rule CTE/WITH is going to be worse performing than the
equivalent view definition - depending on the view is actually used in the
query of course.  They both have their place.  A CTE/WITH is basically a
per-query VIEW though there is an optimization barrier that doesn't allow
the main query WHERE clause to limit the queries like it a view would
normally allow if possible.  Because of this I'll occasionally find need to
specify redundant where clauses inside the CTE to get decent performance on
large tables - mostly for my interactive queries.

David J.




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