Question

Which of the following is a legal expression in SQL ?

a . SELECT NULL FROM EMPLOYEE ;

b SELECT NAME FROM EMPLOYEE ;

C. SELECT NAME FROM EMPLOYEE WHERE SALARY = NULL ;

d SELECT WHERE SALARY IS NULL FROM EMPLOYEE​

Answer 1

Answer:

The correct answer to the question “Which of the following is a legal expression in SQL” is option (b). SELECT NAME FROM EMPLOYEE.

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Answer 2

Answer:

Option(b) and option(c) are legal expressions in SQL:

b SELECT NAME FROM EMPLOYEE ;

C. SELECT NAME FROM EMPLOYEE WHERE SALARY = NULL ;

Explanation:

The SELECT command is used to select the subset of data from the table. You need to specify the fields of the data that you want to be displayed.

a . SELECT NULL FROM EMPLOYEE ;

In this query, you are specifying NULL to select that is not possible. It means this is not a valid SQL query.

b SELECT NAME FROM EMPLOYEE ;

Here, we are specifying NAME filed from the EMPLOYEE table. So it is a legal expression in SQL.

C. SELECT NAME FROM EMPLOYEE WHERE SALARY = NULL ;

Here those employees' names will be displayed whose SALARY is NULL so it is also a legal expression in SQL.

d SELECT WHERE SALARY IS NULL FROM EMPLOYEE​

In this query syntax of the SQL is violated. So it is also not a valid SQL query.

Hence, only option(b) and option(c) are valid and legal expressions in SQL.

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