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SQL performance: Nested select statements.
This is a tip for restructuring nested select statements to make them run faster in SQL server. I can’t vouch for this in all situations, but It shortened a long SQL query for me from 1 hour to 7 minutes.
Where you have
Select * from xyz where id in
(
Select * from abc where id in
(
select id from def
}
)
I recommend re-writing as
Select * into #abcdef from abc where id in
(
select id from def
}
Select * from xyz where id in
(
select id from #abcdef
)
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