MySQL Query for subtracting values from 2 tables - mysql

Question

Hello I have this tables
Table A
ID Name Price QTY
1 name1 1000 10
2 name2 1200 5
Table B
ID Name Price QTY
1 name1 1000 2
I want to achieve
Table C
ID Name Price QTY
1 name1 1000 8
2 name2 1200 5
With my query SELECT DISTINCT ta.name, ta.price,(ta.quantity - tb.quantity) AS quantity, FROM TableA AS ta INNER JOIN TableB AS tb ON ta.id = tb.id
What I get is this
Table C
ID Name Price QTY
1 name1 1000 8
2 name2 1200 3
I sorry I really cant think of a way how to achieve what I want. Thanks for your help.

Answer 1

Your query actually gets you one line instead of two:
-- result set
# name, price, quantity
name1, 1000, 8
Based on your expected output,we can use:
SELECT ta.ID, ta.name, ta.price, ifnull((ta.QTY - tb.QTY),ta.QTY) AS quantity
FROM TableA AS ta
LEFT JOIN TableB AS tb
ON ta.name = tb.name and ta.price=tb.price;
-- result set:
# ID, name, price, quantity
1, name1, 1000, 8
2, name2, 1200, 5
This is the last updated answer I can give you for you updated request.Please consider firing a new question if it does not fulfill.
-- Supposing your latest tables have the following data.
insert TableA values
(1 , 'name1' , 1000 , 10)
,(2 , 'name2' , 1200 , 5);
insert TableB values
(1 , 'name1' , 1000 , 2),
(2 , 'name2', 1000 , 3)
;
-- You probably want this:
SELECT ta.ID, ta.name, ta.price, ifnull((ta.QTY - tb.QTY),ta.QTY) AS quantity
FROM TableA AS ta
LEFT JOIN TableB AS tb
ON ta.name = tb.name and ta.price=tb.price
union
SELECT Id , name , price , QTY
from TableB t
where not exists (select * from TableA where t.name=name and t.price=price)
;
-- result set:
# ID, name, price, quantity
1, name1, 1000, 8
2, name2, 1200, 5
2, name2, 1000, 3