Optimize multiple sql queries into single one

Question

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I want to optimize following three queries into a single query.

SQL

select sum(M.amount) into var1 from t_bill_item M where M.tax =0;
select sum(M.amount) into var2 from t_bill_item M where M.tax =4;
select sum(M.amount) into var3 from t_bill_item M where M.tax =13.5;

var1,var2 and var3 are mysql variables.

Posted 5-Nov-14 23:10pm

Himu from Orissa

Updated 6-Nov-14 0:03am

King Fisher

v4

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Comments

Tomas Takac 6-Nov-14 6:00am

What's the problem with having three separate queries?

Himu from Orissa 6-Nov-14 6:43am

Actually these queries are written in a function which is used in a query. So its taking some long time.

2 solutions

Solution 1

Here is the example

SQL

select 1 as var1
select 2 as var1
select 3 as var1

into

SQL

select *from (select 1 as var1 )t1,(select 2 as var2)t2,(select 3 as var3 )t3

Modify the Query :)

Posted 6-Nov-14 0:06am

King Fisher

Comments

Himu from Orissa 6-Nov-14 6:44am

Here also you are using three selects. Think it wont take less time

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Shweta N Mishra · Accepted Answer · 2014-11-06T01:03:00

Solution 2

You may try this, But would have to check the performance difference between two as data is with you.

SQL

select
sum(Case when M.tax= 0 then M.amount else 0 end) As var1
,sum(Case when M.tax= 4 then M.amount else 0 end) As var2
,sum(Case when M.tax= 13.5 then M.amount else 0 end) As var3
from t_bill_item M where M.tax in (0,4,13.5);

Posted 6-Nov-14 1:03am

Shweta N Mishra

v2

Comments

Himu from Orissa 6-Nov-14 9:48am

seems the one was looking for. Will test it

Shweta N Mishra 7-Nov-14 3:32am

:) Please mark the answer as accepted.