join.sql

join.sql

SELECT * FROM vanorderspecialrequest as a right join th_vanlookupspecialrequests as b on a.idvanspecialrequest = b.id where b.enable = 1;
SELECT * FROM vanorderspecialrequest as a left join th_vanlookupspecialrequests as b on a.idvanspecialrequest = b.id  where b.enable = 1;

# A table (Master) vs B table (non-master)
# A table (1,2,3,4,5) 
# b table ({orderId:1,user:'alpha'},{order:2,user:'beta'})
# if A join B will not deduct the total result

# if B join A will deduct total result

# SQL performance groups by two section 
# 1. sql caculation and 
# 2. total response result.

# Importance need to clear the mysql cache