Other Data Types

This section covers SQL Server data types that do not fall into the common categories of numeric, string, or date/time. These types are essential for handling various specialized data representations.

Binary and Variable-Length Binary Data Types

These data types are used to store binary data, such as images, audio files, or any other sequence of bytes. They are generally more efficient for storing raw binary information than character-based types.

VARBINARY(n) and BINARY(n)

  • VARBINARY(n): Stores variable-length binary data. The n specifies the maximum number of bytes that can be stored, from 1 to 8000.
  • BINARY(n): Stores fixed-length binary data. The n specifies the exact number of bytes stored. If less than n bytes are provided, the data is padded with 0x00 (hexadecimal zeros).

IMAGE (Deprecated)

The IMAGE data type is a synonym for VARBINARY(MAX) and is deprecated. It's recommended to use VARBINARY(MAX) for storing large binary objects.

VARBINARY(MAX)

Stores variable-length binary data with a maximum capacity of 2^31-1 bytes (approximately 2 GB). Suitable for large binary objects (BLOBs).

TIMESTAMP

A data type that exposes automatically generated binary numbers. It is usually used for version-stamping table rows. It does not store date or time. The value is guaranteed to be unique within a table. It is distinct from the TIMESTAMP data type in Oracle.

Note: The TIMESTAMP data type does not store date or time information. It is a synonym for ROWVERSION in SQL Server.

Data Type Description Storage Size
BINARY(n) Fixed-length binary data. n bytes
VARBINARY(n) Variable-length binary data. n bytes + 2 bytes overhead
VARBINARY(MAX) Variable-length binary data up to 2^31-1 bytes. Variable, up to 2 GB
TIMESTAMP (ROWVERSION) Database-wide unique binary number for version stamping. 8 bytes

GUID (Globally Unique Identifier)

A UNIQUEIDENTIFIER is a 128-bit globally unique identifier. It is often used for primary keys or unique identifiers across distributed systems.

UNIQUEIDENTIFIER

  • Stores a 16-byte GUID.
  • Can be generated using functions like NEWID().
  • Example value: '6F9619FF-8B86-11D0-B436-00A0C9224233'

Best Practice: While UNIQUEIDENTIFIER guarantees uniqueness, consider the performance implications for indexing and storage compared to sequential identifiers.

Spatial Data Types

SQL Server supports spatial data types for working with geographical and geometric data. These are typically used in applications involving maps, locations, or geometric modeling.

GEOMETRY

Represents data in either a Euclidean (flat) or non-Euclidean (round-earth) system. It supports points, lines, polygons, and collections of these shapes.

GEOGRAPHY

Represents data in a geographic coordinate system. It is used for data that is referenced to locations on the Earth's surface, such as latitude and longitude points. It also supports points, lines, and polygons.

These types offer a rich set of methods for spatial querying and analysis.

XML Data Type

The XML data type allows you to store XML data directly in a database column. This is highly efficient for applications that heavily rely on XML structures.

XML

  • Stores XML data.
  • Supports methods for querying and manipulating XML documents using XQuery and XML-DML.
  • Can be indexed for performance.

When storing XML, SQL Server preserves the well-formedness and can validate against schemas.

HierarchyID Data Type

The HIERARCHYID data type is used to efficiently store and query hierarchical data. It is ideal for representing tree-like structures, such as organizational charts or file systems.

HIERARCHYID

  • Represents a position within a hierarchy.
  • Supports efficient traversal and querying of the hierarchy.
  • Methods like GetRoot(), GetAncestor(), GetDescendant(), IsDescendantOf() are available.

This data type simplifies complex hierarchical queries that would otherwise require recursive CTEs or complex self-joins.

Table-Valued Parameters and Return Values

While not a single data type in the traditional sense, Table Types are user-defined types that represent the structure of a table. They are used to pass multiple rows of data into stored procedures or functions (Table-Valued Parameters - TVPs) or to return table-like result sets.

User-Defined Table Types

  • Defined using CREATE TYPE statement.
  • Specify the columns and their data types.
  • Can be used as parameters for stored procedures, functions, and as variables.

This feature significantly improves performance by reducing round trips to the server and allowing bulk operations.