Question

Hi I need a query like this

    select count(id) from employee where.. => gives count1=10

    select count(id) from emplyer where..  => gives count2=5

    select count(id) from users where..    => gives count3=20

I can add these result like this

    count = count1+count2+count3;

But I want to know whether there is any option get count using a single query instead of add these result separatly. Also I want to know which one is the best way in case of application perfomance.

Answer 1

You can do

SELECT ((select count(id) from employee where..) + (select count(id) from emplyer where..) + (select count(id) from users where..))

There will hardly be a performance difference – adding three integers is neither a challenge for the MySql nor for the php engine.