Chapter 4, Problem 19CAT

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.

“COUNT” function:

• It is the one function of aggregate function.
• The “COUNT” function is used to compute the number of rows in a table.

Example:

The example for “COUNT” function is given below:

SELECT COUNT(*) FROM STUDENT WHERE MARK_CREDIT >= 90;

The above query is used to display the number of students whose mark credit is greater or equal to “90” by using “COUNT” function.

• From the given query, the asterisk (*) represent any column.
• User can also count the number of rows in a query by selecting a particular column instead of using the asterisk.
  • The below example is as follows

    SELECT COUNT(STUDENT_ID) FROM STUDENT WHERE MARK_CREDIT >= 90;