Multiplication between 2 tables to bring up new field
I have 2 table, for room booking logic.
Calendar
id
room_type_id
date
rate
1,1,2017-12-20,20.00
1,1,2017-12-21,20.00
1,1,2017-12-22,20.00
1,1,2017-12-23,20.00
1,2,2017-12-20,10.00
1,2,2017-12-21,10.00
1,2,2017-12-22,10.00
1,2,2017-12-23,10.00
Calculation
id
room_type_id
adult
child
multiply
1,1,2,0,2 - Room id : 1 - 2 adult 0 child
1,1,2,1,2.5 - Room id : 1 - 2 adult 1 child
1