Group By Clause

In SQL, The Group By statement is used for organizing similar data into groups. 
The data is further organized with the help of equivalent function. 
It means, if different rows in a precise column have the same values, it will arrange those rows in a group.

• The SELECT statement is used with the GROUP BY clause in the SQL query.
• WHERE clause is placed before the GROUP BY clause in SQL.
• ORDER BY clause is placed after the GROUP BY clause in SQL.

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Let's look at how to use the GROUP BY clause with the SUM function in SQL.

 

employee_number	last_name	first_name	salary	dept_id
1001	Smith	John	62000	500
1002	Anderson	Jane	57500	500
1003	Everest	Brad	71000	501
1004	Horvath	Jack	42000	501

SELECT dept_id, SUM(salary) AS total_salaries
FROM employees
GROUP BY dept_id;

There will be 2 records selected. These are the results that you should see:

 

dept_id	total_salaries
500	119500
501	113000

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GROUP BY with the MIN function

employee_number	last_name	first_name	salary	dept_id
1001	Smith	John	62000	500
1002	Anderson	Jane	57500	500
1003	Everest	Brad	71000	501
1004	Horvath	Jack	42000	501

 

SELECT dept_id, MIN(salary) AS lowest_salary FROM employees GROUP BY dept_id;   There will be 2 records selected. These are the results that you should see:

dept_id lowest_salary 500 57500 501 42000

 

Points:

• The GROUP BY Clause is used to group the rows, which have the same values.
• The SELECT statement in SQL is used with the GROUP BY clause.
• In the Group BY clause, the SELECT statement can use constants, aggregate functions, expressions, and column names.
• The GROUP BY Clause is called when the HAVING clause is used to reduce the results.