Oracle Database Foundations

4.3. Group Functions and the GROUP BY Clause

This section explains how you can group rows together and perform some kind of aggregate operation on them. For example, you may want to count the rows for a given condition, calculate the averages of numeric columns, or find the highest or lowest value for a given column in a query result.

aggregate

A type of function in Oracle SQL that performs a calculation or transformation across multiple rows in a table, rather than just on a single row.

The GROUP BY clause fits into the SELECT statement as follows:

SELECT * | {[DISTINCT] column | expression [alias]
         | group_function(column), ...}
  FROM tablename
  [WHERE condition ... ]
  [GROUP BY group_expression, group_expression ...]
  [ORDER BY column [ASC | DESC], ...