MySQL Tutorial

Functions for Use with GROUP BY Clauses

Some functions are designed specifically for use with GROUP BY . These are sometimes called grouping functions or aggregate functions. You can also choose to run these functions over the entire result set of a query, treating all the rows as a single group. We saw this used in queries like this:

select count(*) from employee;

This query will count the number of rows in the employee table.

We typically use these functions over groups, as shown here:

select job, count(job) from employee group by job;

This will tell us how many employees are in each job grouping.

A list of the more useful grouping functions is shown in Table 8.7.

Table 8.7. Grouping Functions

Function

Purpose

avg( column )

Returns the average value in column .

count( column )

Returns the number of values in column .

min( column )

Returns the smallest value in column .

max( column )

Returns the largest value in column .

std( column )

Returns the standard deviation of the values in column .

sum( column )

Returns the sum of values in column .

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