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GROUP BY
The GROUP BY
command is used in SQL to group multiple results and use a totals function on a group of results.
sql
SELECT
column_1,
column_2,
...,
aggregate_function(column_3)
FROM
table_name
GROUP BY
column_1,
column_2,
...;
INFO
This command must always be used after the WHERE
command and before the HAVING
command.
Examples:
sql
SELECT client, SUM(rate)
FROM purchase
GROUP BY client
There are several functions that can be used to manipulate multiple records, these are statistical aggregation functions, the main ones are as follows:
- AVG() to calculate the average of a set of values.
- COUNT() to count the number of rows concerned.
- MAX() to retrieve the highest value.
- MIN() to retrieve the smallest value.
- SUM() to calculate the sum of several lines.