SQL GROUP BY

ROUP BY clause is used to associate an aggregate function with groups of rows.
The SQL GROUP BY clause is used along with the SQL aggregate functions like SUM, COUNT, MAX, MIN, and AVG to provide means of grouping the result by refer to certain database table column.

The SQL syntax for GROUP BY is :

SELECT AGGREGATE FUNCTION ( [COLUMN NAME] )
FROM [TABLE NAME] GROUP BY[COLUMN NAME]

EXAMPLE (WITH SUM) :

We can use GROUP BY clause to calculate sum of the scores by Department.

Table GameScores

PlayerName	Department	Scores
Jason	IT	3000
Irene	IT	1500
Jane	Marketing	1000
David	Marketing	2500
Paul	HR	2000
James	HR	2000

SQL statement :

SELECT Department, SUM(Scores)
FROM GameScores
GROUP BY Department

Result:

Department	SUM(Scores)
HR	4000
IT	4500
Marketing	3500

EXAMPLE (WITH COUNT) :

We can use GROUP BY clause to calculate the number of contestants by Department.

SQL statement :

SELECT Department, COUNT(*)
FROM GameScores
GROUP BY Department

Result:

 

Department	COUNT(*)
HR	2
IT	2
Marketing	2