The Group by Clause
The GROUP BY clause groups the selected rows based on the value of expression
for each row and returns a single row summary information for each group. Suppose
you want to know the average salary of the employees in each department; you can
use SQL function AVG() to list the average salary in each department, enter:
SQL > SELECT DEPTNO, AVG(PAY)
2 FROM EMP
3 GROUP BY DEPTNO;
Other aggregate functions that can be used along with GROUP BY clause are:
<b>COUNT()</b>
sum 0 MAX 0 MIN 0 2.2.9.1 Count() The count function counts the number of non
null number values, distinct number values, or rows selected by the query. For
example, if you wish to know the number of employees listed by their employee
numbers in the EMP table, then enter:
<b>Sum()</b>
The SUM function is used to find the sum or total of the selected values. If
you want to know the sum or salaries paid for various job in an organisation,
then enter:
SQL > SELECT JOB, SUM(PAY) FROM EMP
2 GROUP BY JOB;
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