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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
Practice Problem
Write a query to calculate the average opening price (hint: you will need to use both COUNT
and SUM
, as well as some simple arithmetic.).