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The GROUP BY clause is used to extract only those records that fulfill a specified criterion.

SQL GROUP BY Syntax ::

SQL GROUP BY Syntax

.. code-block:: mysql

SELECT column_name, aggregate_function(column_name)

FROM table_name

| 6 |2011-01-03 | Food |20 |175 |

+---------+--------------+--------------+-------------+----------+

Running the following simple query::

Running the following simple query

.. code-block:: mysql

SELECT userID

FROM activities

However, GROUP BY is much more powerful when used with an aggregate function. Let's say you want to find the total amount spent by each unique User.

You could use the following SQL statement: ::

You could use the following SQL statement:

.. code-block:: mysql

SELECT userID,SUM(ActivityCost) AS "Activity Total"

FROM Activities

With the aggregate SUM() function, SQL can calculate how much each unique user has spent on activities over time.

We can also use the GROUP BY statement on more than one column, like this: ::

We can also use the GROUP BY statement on more than one column, like this:

.. code-block:: mysql

SELECT userID,ActivityDate,SUM(ActivityCost)

FROM Activities