Chapter 4, Problem 7CAT

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.

“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;

“IN” Clause:

• The “IN” clause consists of an “IN” operator followed by a set of values.
• Using an “IN” clause, user can determine whether a column contains one of a particular group of values.

Example:

The example for “IN” clause is given below:

SELECT STUDENT_ID, STUDENT_NAME, STUDENT_CREDIT FROM STUDENT WHERE STUDENT_CREDIT IN(50, 70, 100);

 The above query is used to list student ID, name, and credit for each student with a credit limit of “50”, “70” or “100”.

• From the given query, user can determine whether a student credit limit is “50”, “70” or “100” using an “IN” operator.