Updated: 10 September 2022
User defined variables can be assigned a value in one statement and referred to in another statement.
User variables are written as @var_name
For SET, either = or := can be used as the assignment operator.
User variables can be assigned a value from a limited set of data types: integer, decimal, floating-point, binary or nonbinary string, or NULL.
One way to set a user-defined variable is by issuing a SET statement
SET @var_name = expr [, @var_name = expr] ...
Also see SELECT ... INTO statement.