The name of a parameter or expression can be up to 12 characters long and must be alphanumeric (A-Z, 0-9) beginning with a letter. Parameter and expression names may also contain underscores. (Do not use any keywords, e.g., abs, cos, or tid as the name of a parameter or expression.) You can have up to 400 parameters in any table. A character value can be up to 12 characters. Expressions can be up to 132 characters long.