SQL Server optimized large query with ISNULL where clause -


i have following large select query return 1.5 million rows in 08:15. need optimize query selects 290 columns , can't reduce number of columns improve speed.

select column1 ... column290 dob.table1 (isnull(column50, 1) = 1)

i have read isnull has performance cost if used in where clause because optimizer not use index resort scan, correct?

i trying figure out how rewrite 

where (isnull(column50, 1) = 1)

i tried using cte , setting 

ip_column50 = case when ip_column50 null else ip_column50 end

and rewriting query 

select *  cte  ip_column50 = 1

but cte took longer.

i read approach

if so, consider creating computed column result if isnull(col1, 0) , index computed column , use in where-clause

but not sure how implement this. appreciated optimizing query.

thanks

you can in single query too. this.

select column1 ... column290 dob.table1 column50 = 1 or column50 null

this has potential though of becoming problematic type of catch query. check out article if have multiple criteria need check this.

http://sqlinthewild.co.za/index.php/2009/03/19/catch-all-queries/


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