Creating Groups of Data

GROUP BY Clause Syntax :

• SELECT column, group_function(column) FROM table [WHERE condition] [GROUP BY group_by_expression] [ORDER BY column];

• You can divide rows in a table into smaller groups by using the GROUP BY clause

Using the GROUP BY Clause :

• All columns in the SELECT list that are not in group functions must be in the GROUP BY
  clause
• SELECT deptno, AVG(sal) FROM emp GROUP BY deptno ;

• The GROUP BY column does not have to be in the SELECT list
• SELECT AVG(sal) FROM emp GROUP BY deptno ;

Grouping by More Than One Column :

• You can also group by multiple columns
• Example : select deptno, job, avg(sal) from emp group by deptno, job;