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SQL GROUP BY


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What is SQL GROUP BY?

The SQL GROUP BY is a clause enables SQL aggregate functions for a grouping of information. For example, it could support subtotaling by region number in a sales table.

GROUP BY supports dividing data into sets so that aggregate functions like SUM, AVG and COUNT can be performed.

Why Use SQL GROUP BY?

The SQL GROUP BY clause is used whenever aggregate functions by group are required. This is an aid to understanding and analyzing information.

How To Use SQL GROUP BY

SQL GROUP BY is used as follows. It must follow the FROM and WHERE clauses. The columns in a SELECT clause must be either group by columns or aggregate function columns.

SQL GROUP BY Syntax

 
SELECT <column_name1>, <column_name2> <aggregate_function>
FROM <table_name>
GROUP BY <column_name1>, <column_name2>
 

SQL GROUP BY Example

The following example produces a count of branches by region_nbr from the branch table.

Here are the contents of the table:

Table: BRANCH
branch_nbrbranch_nameregion_nbremployee_count
108New York10010
110Boston1006
212Chicago2005
404San Diego4006
415San Jose4003

This SQL Statement with GROUP BY is executed:

 
SELECT region_nbr, count(*)
FROM branch
GROUP BY region_nbr
ORDER BY region_nbr
 

Here is the result.

region_nbrcount(*)
1002
2001
4002

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