SQL - Data Types


SQL data type is an attribute that specifies type of data of any object. Each column, variable and expression has related data type in SQL.

You would use these data types while creating your tables. You would choose a particular data type for a table column based on your requirement.

SQL Server offers six categories of data types for your use −

Exact Numeric Data Types

bigint -9,223,372,036,854,775,808 9,223,372,036,854,775,807
int -2,147,483,648 2,147,483,647
smallint -32,768 32,767
tinyint 0 255
bit 0 1
decimal -10^38 +1 10^38 -1
numeric -10^38 +1 10^38 -1
money -922,337,203,685,477.5808 +922,337,203,685,477.5807
smallmoney -214,748.3648 +214,748.3647

Approximate Numeric Data Types

float -1.79E + 308 1.79E + 308
real -3.40E + 38 3.40E + 38

Date and Time Data Types

datetime Jan 1, 1753 Dec 31, 9999
smalldatetime Jan 1, 1900 Jun 6, 2079
date Stores a date like June 30, 1991
time Stores a time of day like 12:30 P.M.

Note − Here, datetime has 3.33 milliseconds accuracy where as smalldatetime has 1 minute accuracy.

Character Strings Data Types

DATA TYPE Description
char Maximum length of 8,000 characters.( Fixed length non-Unicode characters)
varchar Maximum of 8,000 characters.(Variable-length non-Unicode data).
varchar(max) Maximum length of 231characters, Variable-length non-Unicode data (SQL Server 2005 only).
text Variable-length non-Unicode data with a maximum length of 2,147,483,647 characters.

Unicode Character Strings Data Types

DATA TYPE Description
nchar Maximum length of 4,000 characters.( Fixed length Unicode)
nvarchar Maximum length of 4,000 characters.(Variable length Unicode)
nvarchar(max) Maximum length of 231characters (SQL Server 2005 only).( Variable length Unicode)
ntext Maximum length of 1,073,741,823 characters. ( Variable length Unicode )

Binary Data Types

DATA TYPE Description
binary Maximum length of 8,000 bytes(Fixed-length binary data )
varbinary Maximum length of 8,000 bytes.(Variable length binary data)
varbinary(max) Maximum length of 231 bytes (SQL Server 2005 only). ( Variable length Binary data)
image Maximum length of 2,147,483,647 bytes. ( Variable length Binary Data)

Misc Data Types

DATA TYPE Description
sql_variant Stores values of various SQL Server-supported data types, except text, ntext, and timestamp.
timestamp Stores a database-wide unique number that gets updated every time a row gets updated
uniqueidentifier Stores a globally unique identifier (GUID)
xml Stores XML data. You can store xml instances in a column or a variable (SQL Server 2005 only).
cursor Reference to a cursor object
table Stores a result set for later processing