MySql : Fetch records from multiple table by arithmetic operations - mysql

Question

I've the following tables :
table_1
------------------
id uid category balance
1 1 A 100
2 2 B 80
table_2
------------------
id uid name
1 1 ABC
2 2 XYZ
table_2
------------------
id uid last_pay
1 1 10
2 1 10
3 1 10
4 2 80
I want to grab records from the three tables and the conditions are as follows :
a) table_1.category = something
b) ( table_1.balance - table_3.SUM(`last_pay`) ) > 0
I want the table_1.category = 'A' because (100 - (10 + 10 + 10)) > 0
Trying this query but its not working :
SELECT t1.uid,t1.category,t1.balance,t2.uid,t2.name FROM table_1 as t1
LEFT JOIN table_2 as t2 ON t1.uid = t2.uid
WHERE t1.category = 2
AND t1.balance - (SELECT SUM(`last_pay`) FROM table_3 WHERE uid = ? )

Answer 1

OK, I give you a full answer with normalized tables:
You can normalize the table_2 and insert the column name to table table_1. See the following and new table structure (with table_1 and table_2):
table_1
--------------------------------------------
id uid category balance name
1 1 A 100 ABC
2 2 B 80 XYZ
table_2
------------------------
id uid last_pay
1 1 10
2 1 10
3 1 10
4 2 80
To create these tables, you can use the following script:
CREATE TABLE table_1 (
`id` INT,
`uid` INT,
`category` VARCHAR(1),
`balance` INT,
`name` VARCHAR(3)
);
INSERT INTO table_1 VALUES
(1, 1, 'A', 100, 'ABC'),
(2, 2, 'B', 80, 'XYZ');
CREATE TABLE table_2 (
`id` INT,
`uid` INT,
`last_pay` INT
);
INSERT INTO table_2 VALUES
(1, 1, 10),
(2, 1, 10),
(3, 1, 10),
(4, 2, 80);
A query to get your expected result:
SELECT t1.uid, t1.category, t1.balance, t2.uid, t1.name
FROM table_1 t1
LEFT JOIN (
SELECT uid, SUM(last_pay) AS last_pay
FROM table_2
GROUP BY uid
) t2 ON t1.uid = t2.uid
WHERE (t1.balance - t2.last_pay) > 0
You can find a working example here: http://sqlfiddle.com/#!9/a2e27/3/0
You want to use your original tables? [answer for original question]
If it is possbile I recommend to normalize the tables! If it is not possible to change the table structure, you can use the following query to get your expected result:
SELECT t1.uid, t1.category, t1.balance, t2.uid, t2.name
FROM table_1 AS t1 LEFT JOIN table_2 AS t2 ON t1.uid = t2.uid
LEFT JOIN (
SELECT uid, SUM(last_pay) AS last_pay
FROM table_3
GROUP BY uid
) t3 ON t1.uid = t3.uid
WHERE (t1.balance - t3.last_pay) > 0
You can find a working example here: http://sqlfiddle.com/#!9/f22024/7/0

Answer 2

Create table/ insert data.
CREATE TABLE table_1
(`id` int, `uid` int, `category` varchar(1), `balance` int)
;
INSERT INTO table_1
(`id`, `uid`, `category`, `balance`)
VALUES
(1, 1, 'A', 100),
(2, 2, 'B', 80)
;
CREATE TABLE table_2
(`id` int, `uid` int, `name` varchar(3))
;
INSERT INTO table_2
(`id`, `uid`, `name`)
VALUES
(1, 1, 'ABC'),
(2, 2, 'XYZ')
;
CREATE TABLE table_3
(`id` int, `uid` int, `last_pay` int)
;
INSERT INTO table_3
(`id`, `uid`, `last_pay`)
VALUES
(1, 1, 10),
(2, 1, 10),
(3, 1, 10),
(4, 2, 80)
;
This query checks for both table_1 categories A and B
And If the table_1.balans is higher then 0 when table_3.last_pay is summed together per category
Query
SELECT
table_1.uid
, table_1.category
, table_1.balance
, table_2.uid
, table_2.name
FROM (
SELECT
uid
, SUM(table_3.last_pay) sum_last_pay
FROM
table_3
GROUP BY
table_3.uid
) AS
table_3_summed
INNER JOIN
table_1
ON
table_1.uid = table_3_summed.uid
INNER JOIN
table_2
ON
table_1.uid = table_2.uid
WHERE
(table_1.balance - table_3_summed.sum_last_pay) > 0
Result
uid category balance uid name
------ -------- ------- ------ --------
1 A 100 1 ABC