using declare in sql code example

Example 1: how to declare a variable in sql

DECLARE @COURSE_ID AS INT, @COURSE_NAME VARCHAR (10);

Example 2: what does declare do in sql

-- MySQL

DECLARE variable_name datatype(size) [DEFAULT default_value];
-- Declaring a variable without specifying a default value will result it
-- in being a null value.
-- Declare is what allows us to create a variable