sql server - How to increase the performance of sql query that contains a lot of joins and union -


i have created procedure in following way,

create procedure proc_foo  begin declare @somevar int set @somevar=0 if exists (select column1 tbl1) begin set @somevar = 1 end if exists (select column2 tbl2) begin set @somevar = 1 end .... ... .... if exists (select columnn tbln) begin set @somevar = 1 end if(@somevar =1) begin  select count(column1) tbl1  union  select count(column2) tbl2  union  ...  ...  ...  select count(columnn) tbln  end end

the select statements contains lot of joins , taking lot of time execute.can explain me different approach more faster.

i first suggest use "with recompile" hint on stored procedure. recompile sp , generate new execution plan based on how variable ends being set. fresh execution plan every time.

additionally, adding indexes on columns joining on , use include columns if creating non-clustered indexes columns you're outputting.


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