Data Types

DECIMAL and NUMERIC

Fixed precision and scale decimal numbers. DECIMAL and NUMERIC are functionally equivalent.

Syntax:

DECIMAL ( precision [ , scale] )
NUMERIC ( precision [ , scale] )

Examples:

SELECT CAST(123 AS DECIMAL(5,2)) --returns 123.00
SELECT CAST(12345.12 AS NUMERIC(10,5)) --returns 12345.12000

FLOAT and REAL

Approximate-number data types for use with floating point numeric data.

SELECT CAST( PI() AS FLOAT) --returns 3.14159265358979
SELECT CAST( PI() AS REAL) --returns 3.141593

Integers

Exact-number data types that use integer data.

Data type	Range	Storage
bigint	-2^63 (-9,223,372,036,854,775,808) to 2^63-1 (9,223,372,036,854,775,807)	8 Bytes
int	-2^31 (-2,147,483,648) to 2^31-1 (2,147,483,647)	4 Bytes
smallint	-2^15 (-32,768) to 2^15-1 (32,767)	2 Bytes
tinyint	0 to 255	1 Byte

MONEY and SMALLMONEY

Data types that represent monetary or currency values.

Data type	Range	Storage
money	-922,337,203,685,477.5808 to 922,337,203,685,477.5807	8 bytes
smallmoney	-214,748.3648 to 214,748.3647	4 bytes

BINARY and VARBINARY

Binary data types of either fixed length or variable length.

Syntax:

BINARY [ ( n_bytes ) ]
VARBINARY [ ( n_bytes | max ) ]

n_bytes can be any number from 1 to 8000 bytes. max indicates that the maximum storage space is 2^31-1.

Examples:

SELECT CAST(12345 AS BINARY(10)) -- 0x00000000000000003039
SELECT CAST(12345 AS VARBINARY(10)) -- 0x00003039

CHAR and VARCHAR

String data types of either fixed length or variable length.

Syntax:

CHAR [ ( n_chars ) ]
VARCHAR [ ( n_chars ) ]

Examples:

SELECT CAST('ABC' AS CHAR(10)) -- 'ABC       ' (padded with spaces on the right)
SELECT CAST('ABC' AS VARCHAR(10)) -- 'ABC' (no padding due to variable character)
SELECT CAST('ABCDEFGHIJKLMNOPQRSTUVWXYZ' AS CHAR(10))  -- 'ABCDEFGHIJ' (truncated to 10 characters)

NCHAR and NVARCHAR

UNICODE string data types of either fixed length or variable length.

Syntax:

NCHAR [ ( n_chars ) ]
NVARCHAR [ ( n_chars | MAX ) ]

Use MAX for very long strings that may exceed 8000 characters.

UNIQUEIDENTIFIER

A 16-byte GUID / UUID.

DECLARE @GUID UNIQUEIDENTIFIER = NEWID(); 
SELECT @GUID -- 'E28B3BD9-9174-41A9-8508-899A78A33540'
DECLARE @bad_GUID_string VARCHAR(100) = 'E28B3BD9-9174-41A9-8508-899A78A33540_foobarbaz'
SELECT 
    @bad_GUID_string,   -- 'E28B3BD9-9174-41A9-8508-899A78A33540_foobarbaz'
    CONVERT(UNIQUEIDENTIFIER, @bad_GUID_string) -- 'E28B3BD9-9174-41A9-8508-899A78A33540'