String literals are specified by one or more characters enclosed in single quotes. The default data type for string literals is varchar, but a string literal can be assigned to any character data type or to money or date data type without using a data type conversion function.

To compare a string literal with a non-character data type, you must either cast the string literal to the non-character data type or cast the non-character data type to the string literal type. Failure to do so causes unexpected results if the non-character data type contains the ‘NULL (0) value.