Chapter 4, Problem 18CAT

Program Plan Intro

“SELECT” command:

The “SELECT” command is used to retrieve data in a database.

Syntax for selecting values from the table is as follows:

SELECT STUDENT_ID FROM STUDENT;

• The given query is used to display each student ID from “STUDENT” table.

“SUM” function:

• It is the one function of aggregate function.
• The “SUM” function is used to compute the total of the values in a column.

Example:

The example for “SUM” function is given below:

SELECT SUM(MARK_CREDIT) FROM STUDENT;

The above query is used to display the sum of all students mark credit from “STUDENT” table using “SUM” function.

“GROUP BY” Clause:

• User can group the data using “GROUP BY” clause.
• This clause allows the user to group data on a specific column and then computes statistics when user preferred.

Example:

The example for “GROUP BY” clause is given below:

SELECT CUSTOMER_NAME, SUM(AMOUNT) FROM CUSTOMERS GROUP BY CUSTOMER_NAME;

The above query is used to list the customer name and the sum of amount using “GROUP BY” clause.

“HAVING” Clause:

• The “HAVING” clause is used to restrict the groups that are included.
  • This restriction does not apply to individual rows but relatively apply to groups.

Example:

The example for “HAVING” clause is given below:

SELECT STUDENT_ID, NAME, AGE, ADDRESS, TOTAL_MARK FROM STUDENTS GROUP BY AGE HAVING COUNT(AGE) >= 10;

• The above query is used to display a record for a similar age count that would be more than or equal to “10”.