How do I make this query fast? It reaches time out anytime I run it in the SQL Server database - sql

Question

SELECT firstpartno, nOccurrence, nMale, nFemale, COUNT(nMale) / CAST
((SELECT SUM(nOccurrence) AS Expr1
FROM (SELECT COUNT(dbo.vw_Tally1.nMale) AS nOccurrence
FROM dbo.vw_Split4) AS SumTally) AS decimal) AS nMProportion, COUNT(nFemale) / CAST
((SELECT SUM(nOccurrence) AS Expr1
FROM (SELECT COUNT(dbo.vw_Tally1.nFemale) AS nOccurrence
FROM dbo.vw_Split4 AS vw_Split4_1) AS SumTally_1) AS decimal) AS nFProportion
FROM dbo.vw_Tally1
GROUP BY firstpartno, nOccurrence, nMale, nFemale

Answer 1

If i understood your question here's the solution for you :
SELECT
firstpartno
,nOccurrence
,nMale
,nFemale
,CASE WHEN SUM_nOccurrence.SUM_nOccurrenceMale = 0
THEN 0
ELSE COUNT(nMale)/SUM_nOccurrence.SUM_nOccurrenceMale
END AS nMProportion
,CASE WHEN SUM_nOccurrence.nOccurrenceFemale = 0
THEN 0
ELSE COUNT(nFemale)/SUM_nOccurrence.nOccurrenceFemale
END AS nFProportion
FROM
dbo.vw_Tally1
LEFT JOIN
(SELECT
CAST(SUM(nOccurrenceMale)AS decimal) AS SUM_nOccurrenceMale
,CAST(SUM(nOccurrenceFemale)AS decimal) AS SUM_nOccurrenceFemale
FROM (SELECT
COUNT(dbo.vw_Tally1.nMale) AS nOccurrenceMale
,COUNT(dbo.vw_Tally1.nFemale) AS nOccurrenceFemale
FROM dbo.vw_Split4 ) AS SumTally) SUM_nOccurrence
ON 1=1
GROUP BY
firstpartno
,nOccurrence
,nMale
,nFemale
I hope this will help you
Good Luck :)

Answer 2

The query looks dubious to say the least. You select all records of table vw_Tally1. For each of these records you do the following:
select COUNT(vw_Tally1.nMale) from table vw_Split4. This is COUNT(*) of vw_Split4 when vw_Tally1.nMale is not null, otherwise it is null.
Then you sum this value. Which makes no sense, as the sum of a value is the value itself.
You do the same for nFemale.
At last you group by (firstpartno, nOccurrence, nMale, nFemale) and use the values found so strangly to calculate something. As you don't aggregate the found values, you get a random match per group. I.e. the dbms takes one of the matching records. As nMale and nFemale are grouping columns, the values are constant for all records of the group. So no big problem, but a lot of useless work.
So to speed this up, first think of what you want to select actually. This looks like to become a very simple select statement in the end. We can help you, if you tell us what your tables contain, what result set you are after, what does nMale and nFemale stand for, and what are the primary keys or unique columns of the tables involved.