Update column with the sum of column in previous rows in MySQL

We have a table, essentially:

id, amount, end balance, account_id

I now want to re-calculate the end balance values (because of possible corruption)

End balance is basically "end balance of previous entry with the same account_id" + amount.

Assume that there are a lot of entries, but I want to do this for one account at a time (or for a couple of accounts).

(So, if we have the corrupt table:

Id  Amount Balance Account
1     100       0     1
2     100     100     2
3     -40     -40     1
4     100      60     1

I want the resulting db table to be:

Id  Amount Balance Account
1     100     100     1
2     100     100     2
3     -40      60     1
4     100     160     1

)

Let make the table called nuoji and load it with the above data

USE test
DROP TABLE IF EXISTS nuoji;
CREATE TABLE nuoji
(
  id int not null auto_increment primary key,
  amount INT NOT NULL,
  balance INT NOT NULL,
  account INT NOT NULL,
  KEY (account)
) ENGINE=MyISAM;
INSERT INTO nuoji (amount,balance,account) VALUES
(100,100,1),(100,100,2),(-40,-40,1),(100,60,1);
SELECT * FROM nuoji;

Let's run that code and Make the Data:

mysql> USE test
Database changed
mysql> DROP TABLE IF EXISTS nuoji;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE nuoji
    -> (
    ->   id int not null auto_increment primary key,
    ->   amount INT NOT NULL,
    ->   balance INT NOT NULL,
    ->   account INT NOT NULL,
    ->   KEY (account)
    -> ) ENGINE=MyISAM;
Query OK, 0 rows affected (0.05 sec)

mysql> INSERT INTO nuoji (amount,balance,account) VALUES
    -> (100,100,1),(100,100,2),(-40,-40,1),(100,60,1);
Query OK, 4 rows affected (0.00 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM nuoji;
+----+--------+---------+---------+
| id | amount | balance | account |
+----+--------+---------+---------+
|  1 |    100 |     100 |       1 |
|  2 |    100 |     100 |       2 |
|  3 |    -40 |     -40 |       1 |
|  4 |    100 |      60 |       1 |
+----+--------+---------+---------+
4 rows in set (0.00 sec)

mysql>

Here is the Query You Need

SET @rt=0; SET @ndx=0; SET @given_account=1;
UPDATE nuoji A INNER JOIN  (SELECT * FROM
(SELECT (@ndx:=@ndx+1) ndx,id,amount,
(@rt:=@rt+amount) newbalance FROM nuoji
WHERE account=@given_account) BB) B USING (id)
SET A.balance=B.newbalance;

Here is that Query Executed:

mysql> SET @rt=0; SET @ndx=0; SET @given_account=1;
Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.00 sec)

mysql> UPDATE nuoji A INNER JOIN  (SELECT * FROM
    -> (SELECT (@ndx:=@ndx+1) ndx,id,amount,
    -> (@rt:=@rt+amount) newbalance FROM nuoji
    -> WHERE account=@given_account) BB) B USING (id)
    -> SET A.balance=B.newbalance;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 3  Changed: 0  Warnings: 0

mysql> SELECT * FROM nuoji;
+----+--------+---------+---------+
| id | amount | balance | account |
+----+--------+---------+---------+
|  1 |    100 |     100 |       1 |
|  2 |    100 |     100 |       2 |
|  3 |    -40 |      60 |       1 |
|  4 |    100 |     160 |       1 |
+----+--------+---------+---------+
4 rows in set (0.00 sec)

mysql>

That's it !!!

If other accounts are messed up in the same way, set @given_account, and then execute the code.

Here is That Code Formatted:

SET @rt = 0;
SET @ndx = 0;
SET @given_account = 1;
UPDATE
    nuoji A INNER JOIN
    (
        SELECT * FROM
        (
            SELECT
                (@ndx:=@ndx+1) ndx,id,
                amount,(@rt:=@rt+amount) newbalance
            FROM nuoji
            WHERE account=@given_account
        ) BB
    ) B USING (id)
SET A.balance=B.newbalance;

Give it a Try !!!

StackExchange Database Administrators Q#56378, answer score: 3