# SQL SUM

**Starting here?** This lesson is part of a full-length tutorial in using SQL for Data Analysis. Check out the beginning.

## The SQL SUM function

`SUM`

is a SQL aggregate function that totals the values in a given column. Unlike `COUNT`

, you can only use `SUM`

on columns containing numerical values.

The query below selects the sum of the `volume`

column from the Apple stock prices dataset:

```
SELECT SUM(volume)
FROM tutorial.aapl_historical_stock_price
```

An important thing to remember: **aggregators only aggregate vertically**. If you want to perform a calculation across rows, you would do this with simple arithmetic.

You don’t need to worry as much about the presence of nulls with `SUM`

as you would with `COUNT`

, as `SUM`

treats nulls as 0.

### Sharpen your SQL skills

`COUNT`

and `SUM`

, as well as some simple arithmetic.).