A constant, or literal, is a symbol that represents a specific value of a specific data type. Constants or literals are used commonly as the default values for table columns, variables, and parameters. The format of constant or literal depends on the data type of the value it represents. There are x formats used to specify literals in SQL Server:

* Integer Number Literals - Strings of numbers prefixed with (+/-) as the sign if needed. They are used for integer data types. For example: -2255.

* Decimal Number Literals - Strings of numbers with a single decimal point and an optional prefix sign (+/-). They are used for DECIMAL data type. For example: 1894.1204.

* Floating Point Number Literals - Numeric values represented in the scientific notation. They are used for FLOAT data type. For example: 9.22337e+010.

* Character String Literals - Strings of characters enclosed in single quotes. They are used for character string data types. . For example: 'Welcome to GlobalGuideLine.com!'.

* Unicode Character String Literals - Strings of Unicode characters enclosed in single quotes with a prefix of (N). They are used for Unicode character string data types. For example: N'Welcome to GlobalGuideLine.com'.