In the below queries which gives better performance

Question

Hi All,
In the below two queries which gives better performance.
Requirement is I need to find if all the 3 score columns are null then I need to assign -ve value -9999 else some +ve value 2
1)
select case when count(CUST_score1)+count(CUST_score2)+count(CUST_score3)=0 then -111111'
else 11 end
from
customer
where subscriber_id=1050
and cust_system_code='1882484'
2)
select case whenCUST_score1 is null and CUST_score2 is null and CUST_score3 is null then '-9999'
else '11' end
from
customer
where subscriber_id=1050
and cust_system_code='1882484'
Please help, because we have more data in table customer so I need to confirm which is better.
Regards,
Chanda

Answer 1

user546757 wrote:
Hi All,
In the below two queries which gives better performance.
Requirement is I need to find if all the 3 score columns are null then I need to assign -ve value -9999 else some +ve value 2
1)
select case when count(CUST_score1)+count(CUST_score2)+count(CUST_score3)=0 then -111111'
else 11 end
from
customer
where subscriber_id=1050
and cust_system_code='1882484'
2)
select case whenCUST_score1 is null and CUST_score2 is null and CUST_score3 is null then '-9999'
else '11' end
from
customer
where subscriber_id=1050
and cust_system_code='1882484'
Please help, because we have more data in table customer so I need to confirm which is better.
Regards,
ChandaThe two statements aren't equivalent. If you know that your where condition is restricting to a single row then there is no point in doing a count as that will introduce an additional aggregate function that isn't required for a single row. If you are dealing with multiple rows from the where condition then the second query will return multiple rows whereas the first query returns 1 row, so they don't do the same thing anyway.