How to update one table based on another one? - php

Question

I have these two tables:
// user
+----+-------+------------+
| id | name | total_rep |
+----+-------+------------+
| 1 | Jack | 100 |
| 2 | Peter | 334 |
| 3 | John | 1 |
| 4 | Ali | 5463 |
+----+-------+------------+
// rep
+----+------------+---------+------+
| id | reputation | id_user | done |
+----+------------+---------+------+
| 1 | 5 | 2 | 1 |
| 2 | 2 | 3 | 1 |
| 3 | 15 | 2 | Null |
| 4 | 10 | 2 | Null |
| 5 | 5 | 4 | 1 |
| 6 | 10 | 3 | Null |
+----+------------+---------+------+
I'm trying to sum the number of reputation column from rep table where done is Null for specific user and then add it to total_rep column from user table. So it is expected output:
// specific user
$id = 2;
// user
+----+-------+------------+
| id | name | total_rep |
+----+-------+------------+
| 1 | Jack | 100 |
| 2 | Peter | 359 | -- this is updated
| 3 | John | 1 |
| 4 | Ali | 5463 |
+----+-------+------------+
Note: Then I will update done column and set all Null values for that user to 1. (this is not my question, I can do that myself)
How can I do that?

Answer 1

One way to do it is to use the result of a subquery as a scalar value in an update statement.
UPDATE `user`
SET total_rep = total_rep + (
SELECT SUM(reputation) AS rep_sum FROM `rep` WHERE done IS NULL AND id_user = 2)
WHERE id = 2;

Answer 2

You can't update two tables in one statement, so you will need to execute a transaction. Or maybe in some code do the next thing I'll make it in PHP
$query_result=DB::select('Select sum(reputation) as reputation, id_user from rep where done is null group by id_user');
foreach($query_result as $result){
//update the data
}
You have to take the data and update firstable the reputation table to clean it and then the user table to sum the rep values