Difference between revisions of "Running Total"

In this example you are shown how to get a running total in a set of results.

Table 1 shows the results without the running total and Table 2 shows what we get with the running total.

Table 1
whndescriptionamount
2006-11-01Wages50
2006-11-02Company Store-10
2006-11-03Company Store-10
2006-11-04Company Store-10
2006-11-05Company Store-10
2006-11-06Company Store-10
Table 2
whndescriptionamount
2006-11-01Wages50
2006-11-02Company Store-10
2006-11-03Company Store-10
2006-11-04Company Store-10
2006-11-05Company Store-10
2006-11-06Company Store-10
schema:scott
```DROP TABLE transact
```
``` CREATE TABLE transact(
whn DATE,
description VARCHAR(20),
amount TEXT );
INSERT INTO transact VALUES ('2006-11-01','Wages',50);
INSERT INTO transact VALUES ('2006-11-02','Company Store',-10);
INSERT INTO transact VALUES ('2006-11-03','Company Store',-10);
INSERT INTO transact VALUES ('2006-11-04','Company Store',-10);
INSERT INTO transact VALUES ('2006-11-05','Company Store',-10);
INSERT INTO transact VALUES ('2006-11-06','Company Store',-10);
```

To calculate a running total a table needs to be joined to itself, each version can be called table x and table y.

```SELECT x.whn, x.description, x.amount,
SUM(y.amount) AS balance
FROM transact x JOIN transact y ON (x.whn>=y.whn)
GROUP BY x.whn, x.description, x.amount
```

If you want the money IN and money OUT to be separate a `CASE` expression can be used.

```SELECT w AS dte, d AS description,
CASE WHEN (a>=0) THEN a ELSE NULL END AS moneyIN,
CASE WHEN (a<0) THEN a ELSE NULL END AS moneyOUT,
balance FROM
(SELECT x.whn AS w, x.description AS d,
x.amount AS a, SUM(y.amount) AS balance
FROM transact x JOIN transact y ON (x.whn>=y.whn)
GROUP BY x.whn, x.description, x.amount) t
```