Variables and SET statements in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a variable in SQL?

A variable in SQL is a named storage that holds a value temporarily during the execution of a batch or procedure.

beginner

How do you declare a variable in SQL?

You declare a variable using the DECLARE statement, for example: <br>DECLARE @myVar INT;

beginner

What does the SET statement do in SQL?

The SET statement assigns a value to a variable, for example: <br>SET @myVar = 10;

intermediate

Can you assign a value to a variable during declaration in SQL?

No, in standard SQL you declare a variable first and then assign a value using SET. Some SQL dialects allow assignment during declaration, but it's not standard.

intermediate

What is the difference between SET and SELECT for assigning variables?

SET assigns one variable at a time and is standard. SELECT can assign multiple variables at once but may behave differently if no rows are returned.

Which SQL statement is used to declare a variable?

A DECLARE

B SET

C SELECT

D CREATE

DECLARE is used to create a variable in SQL.

How do you assign the value 5 to a variable named @count?

A SET @count = 5;

B DECLARE @count = 5;

C SELECT @count = 5;

D CREATE @count = 5;

SET assigns a value to an already declared variable.

Which statement is true about SET and SELECT for variable assignment?

A SET can assign multiple variables at once.

B Both SET and SELECT cannot assign variables.

C DECLARE assigns values to variables.

D SELECT can assign multiple variables at once.

SELECT can assign multiple variables in one statement.

What happens if you use SET to assign a variable but the value is missing?

A The variable is set to NULL.

B The variable keeps its previous value.

C An error occurs.

D The variable is deleted.

SET requires a value; missing value causes an error.

Which of these is a valid variable name in SQL?

A totalAmount

B @totalAmount

C #totalAmount

D $totalAmount

Variables in SQL typically start with @.

Explain how to declare and assign a value to a variable in SQL using SET statements.

Think about the two-step process: first create the variable, then give it a value.

Describe the difference between SET and SELECT when assigning values to variables.

Consider how many variables each can assign and what happens if no data is returned.