Using Group Functions in the SELECT Clause in SQL Server

Q

How To Use Group Functions in the SELECT Clause in SQL Server?

✍: FYIcenter.com

A

If group functions are used in the SELECT clause, all rows that meet the criteria defined in the WHERE clause will be treated as a single group. The group functions will be apply all rows in that group as a whole. The final output of the SELECT statement is the resulting values of the group functions, not the rows in the group.

Here are two good examples of using group functions :

SELECT COUNT(*), MAX(counts), MIN(created) 
   FROM fyi_links
GO
COUNT(*) MAX(counts)  MIN(created)
7        972          2003-01-01

SELECT COUNT(*), MAX(counts), MIN(created) 
   FROM fyi_links WHERE tag = 'DBA'
GO
COUNT(*) MAX(counts)  MIN(created)
3        972          2005-01-01

In first case, the group contains all the rows in table fyi_links, because is no WHERE clause. In the second case, the group contains only 3 rows because of the WHERE clause tag = 'DBA'.

 

Using SELECT Statements and GROUP BY Clauses in SQL Server

⇒⇒SQL Server Database Tutorials

2016-10-25, 599👍, 0💬