Top 20 interview questions and answers for SQL scalar functions and table-valued functions

What is a scalar function in SQL?

 A scalar function is a user-defined function that returns a single value based on the input parameters.

How to create a scalar function in SQL?

To create a scalar function, use the CREATE FUNCTION statement with the RETURNS clause to specify the return data type and the function's logic.

What is a table-valued function in SQL?

A table-valued function is a user-defined function that returns a table as a result set. It can be used in the FROM clause of a SELECT statement.

How to create a table-valued function in SQL?

To create a table-valued function, use the CREATE FUNCTION statement with the RETURNS TABLE clause to define the columns of the returned table and the function's logic.

What is the difference between a scalar function and a table-valued function?

 A scalar function returns a single value, whereas a table-valued function returns a table as a result set.

Can a scalar function call a table-valued function?

 Yes, a scalar function can call a table-valued function as part of its logic.

How to call a scalar function in SQL?

To call a scalar function, use the function name followed by parentheses, providing the necessary input parameters.

How to call a table-valued function in SQL?

To call a table-valued function, use the function name as a table in the FROM clause of a SELECT statement, specifying any required input parameters.

What are the advantages of using scalar functions?

Scalar functions can encapsulate complex logic, improve code reusability, and enhance readability by abstracting complex calculations into a single function call.

What are the advantages of using table-valued functions?

Table-valued functions can simplify querying by encapsulating complex logic, provide a reusable result set, and improve performance by allowing the optimizer to work more efficiently.

Can scalar functions modify data in the database?

 No, scalar functions are read-only and cannot modify data in the database.

Can table-valued functions modify data in the database?

Table-valued functions can be used to modify data if they are defined as inline table-valued functions and include appropriate UPDATE, INSERT, or DELETE statements.

What is the difference between an inline table-valued function and a multi-statement table-valued function?

An inline table-valued function is defined with a single SELECT statement, while a multi-statement table-valued function uses multiple statements to populate the result set.

Can a table-valued function be used in a JOIN operation?

Yes, a table-valued function can be used in a JOIN operation by referencing it in the FROM clause and specifying the necessary JOIN conditions.

Can a scalar function be used in a WHERE clause?

Yes, a scalar function can be used in a WHERE clause to filter rows based on the function's return value.

Can table-valued functions return different result sets based on input parameters?

Yes, table-valued functions can be designed to return different result sets based on the input parameters provided during the function call.

Can scalar functions return NULL values?

Yes, scalar functions can return NULL values if the logic within the function results in a NULL value.

Can table-valued functions have input parameters?

Yes, table-valued functions can have input parameters that can be used to filter or modify the returned result set.

Can scalar functions be used in computed columns?

Yes, scalar functions can be used in computed columns to perform calculations and return a value based on other column values.

Can table-valued functions be used in subqueries?

Yes, table-valued functions can be used in subqueries to generate dynamic result sets that can be further processed in the main query.