Sum 3 Tables and Subtract the User Request - php

Question

Hello Developers/Programmers
I am working on withdrawal function on my website.
So it goes like this
I need to total the 3 tables i have by User ID with status of '1' ,and Subtract the Inputed amount by the User Requested the Withdrawal
These are my 3 tables
tbl_bonus_1
id | amount | user_id | status
1 20 1 1
2 20 1 1
3 20 3 1
tbl_bonus_2
id | amount | user_id | status
1 30 1 1
2 30 1 1
3 30 3 1
tbl_bonus_3
id | amount | user_id | status
1 40 1 1
2 40 1 1
3 40 3 1
Now I need to get all that 3 tables by USER ID and get the total of it.
After getting the total i need to subtract the Inputted quantity of the USER
and update the status to 0 so that the user cant withdraw again.
Im using Codeigniter 3.1.5

Answer 1

select user_id, sum(amount)
from
(select * from tbl_bonus_1
union
select * from tbl_bonus_2
union
select * from tbl_bonus_3) tt
where status = 1
group by user_id
DEMO:
http://sqlfiddle.com/#!9/7f1807e/1
And UPDATE (single user):
UPDATE tbl_bonus_1 t1 INNER JOIN tbl_bonus_2 t2
ON t1.user_id = t2.user_id
INNER JOIN tbl_bonus_3 t3
ON t1.user_id = t3.user_id
SET t1.amount = 0, t2.amount = 0, t3.amount = 0
WHERE t1.user_id = 1;

Answer 2

Realistically, you don't want to subtract from these tables if you want to manage a balance. You need to add a 4th table that is withdrawal amount, so you can capture the transactions. If you have a total of 160 across 3 tables, and the user withdrawals 150, how would you determine which to decrement.
I would suggest actually consolidating all of these into 1 trasaction table, and capture the amounts there.
So to get what you need you will need to leverage variables which will need to be passed to the query. Below will give you what you are asking for. That being said, this is not the correct way to do this. Also, there is no way to determine which of the 3 balances you want to subtract the withdraw from. This is just not how transaction ledgers work and for a lot of reasons I am not going to get in to right now. At the bottom of this answer is how I suggest you should build your table. You will be able to get information with more easy while capturing more/better data.
How to get data from current structure:
set #withdraw = 150.00, #user = 1;
select user_id, sum(amount) as prevBalance
, #remainingBalance := if(#user = user_id,sum(amount)-#withdraw,sum(amount)) as remainingBalance
from
(select * from tbl_bonus_1
union
select * from tbl_bonus_2
union
select * from tbl_bonus_3) balance
group by user_id;
How you should build your schema:
CREATE TABLE ledger (id int NOT NULL AUTO_INCREMENT
,user_id int
, amount decimal(5,2)
, transaction_type varchar(20)
,PRIMARY KEY (ID));
INSERT INTO ledger VALUES
(null,1,20,'Bonus1'),
(null,1,20,'Bonus1'),
(null,3,20,'Bonus1'),
(null,1,30,'Bonus2'),
(null,1,30,'Bonus2'),
(null,3,30,'Bonus2'),
(null,1,40,'Bonus3'),
(null,1,40,'Bonus3'),
(null,3,40,'Bonus3'),
(null,1,-150,'Withdraw')
;
Then all you would need to do is run the following query.
select user_id, sum(amount) balance from ledger
group by user_id;