How to check if a variable is already declared (T-SQL)?

Question

When I write

DECLARE @x INT

Is there a way to check whether the variable @x has already been declared or not?

Answer 1

IF you try to access a variable that has not yet been defined, the T-SQL Script will give you an error telling you the variable isn't defined.

Msg 137, Level 15, State 2, Line 5 Must declare the scalar variable "@x".