Question

How does grouping work with some of the built-in SQL functions

Answer 1

SQL has numerous built-in aggregate functions such as COUNT, MAX, MIN, AVG etc. The GROUP BY clause specifies how to group rows from a data table when aggregating information.

For example following SQL statement would give count of all students:

SELECT COUNT(*)

FROM STUDENTS;

But by using GROUP BY, counts acording to degree can be found:

SELECT DEGREE, COUNT(*)

FROM STUDENTS

GROUP BY DEGREE;

The attribute which forms basis of grouping should be included in GROUP BY clause. Then SQL groups record on basis of the attributes mentioned in group by clause and performs required functions.

Another example is to get total salaries paid in each department.

SELECT DEPARTMENT, SUM(SALARY)

FROM EMPLOYEES

GROUP BY DEPARTENT;