SQL GROUP BY Clause

The SQL GROUP BY Clause is used along with the group functions to retrieve data grouped according to one or more columns.

For Example: If you want to know the total amount of salary spent on each department, the query would be:

SELECT dept, SUM (salary)
FROM employee
GROUP BY dept;

The output would be like:

dept salary
---------------- --------------
Electrical 25000
Electronics 55000
Aeronautics 35000
InfoTech 30000

NOTE: The group by clause should contain all the columns in the select list expect those used along with the group functions.

SELECT location, dept, SUM (salary)
FROM employee
GROUP BY location, dept;

The output would be like:

location dept salary
------------- --------------- -----------
Bangalore Electrical 25000
Bangalore Electronics 55000
Mysore Aeronautics 35000
Mangalore InfoTech 30000