To declare a local variable’s name and datatype use:
declare @variable_name datatype [, @variable_name datatype]...
The variable name must be preceded by the @ sign and conform to the rules for identifiers. Specify either a user-defined datatype or a system-supplied datatype other than text, image, or sysname.
In terms of memory and performance, this is more efficient:
declare @a int, @b char(20), @c float
than this:
declare @a int declare @b char(20) declare @c float
