sql server - SQL add filter only if a variable is not null -

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hi have query follows:

    select  route_id [route_id]     route_master(nolock)      route_ou = 2     ,   route_query = @l_s_query     ,   lang_id  = 1

here, " , route_query = @l_s_query" condition in clause should added when @l_s_query non empty. donot want write if else condition @l_s_query. there way handle in clause directly.thanks.

you can translate requirement :

select  route_id [route_id] route_master(nolock)  route_ou = 2 ,   (@l_s_query null or route_query = @l_s_query) ,   lang_id  = 1 option (recompile)

the option (recompile) optional can give better execution plans @ expense of compilation time discussed in canonical article on topic dynamic search conditions in t‑sql

or coalesce() avoid or :

where  route_ou = 2 ,   coalesce(@l_s_query,route_query) = route_query  ,   lang_id  = 1

note: @jarlh said, if route_query nullable, may cause issues becuase of null comparison, may want use first query.

another option of 2 separate queries using union all , 1 each condition -

select .. ..  @l_s_query null union select .. ..  @l_s_query = route_query

on terms of performance,only last 1 use index, believe first 1 fastest, may change depanding on indexes, sizes of tables etc..


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