Data Types in SQL Server

Understanding SQL data types is fundamental for any database developer. Every column in a database table requires both a name and a specified data type. The data type serves as a guide for SQL, indicating the nature of the data within each column and determining how SQL interacts with it.

SQL Server Data Types

In MySQL, data types are primarily categorized into three groups: string, numeric, and date and time.

String Data Types

Data TypeDescriptionStorage
charFixed-width character stringDefined by data (up to 8,000 bytes)
varcharVariable-width character stringLength of data (up to 8,000 bytes)
textVariable-width character string (large)2GB of text data
ncharFixed-width Unicode character stringDefined by data (up to 4,000 characters)
nvarcharVariable-width Unicode character stringLength of data (up to 4,000 characters)
ntextVariable-width Unicode character string (large)2GB of text data

Character string data types in SQL Server store character-based data. char and nchar are fixed-width, while varchar and nvarchar are variable-width. The text and ntext data types are used for storing large amounts of text data. The Unicode variants (nchar, nvarchar, ntext) support Unicode character sets.

Numeric Data Types

Data TypeDescriptionStorage
bigintLarge integer8 bytes
numericFixed precision and scale numbers5-17 bytes
bitBit-value type1 byte
smallintSmall integer2 bytes
decimalFixed precision and scale numbers5-17 bytes
smallmoneyMonetary data4 bytes
intInteger4 bytes
tinyintVery small integer1 byte
moneyMonetary data8 bytes

These exact numeric data types provide a range of options for representing whole numbers and fixed precision values in SQL Server.

Approximate numerics

Data TypeDescriptionStorage
floatFloating-point number4 or 8 bytes
realFloating-point number4 bytes

The approximate numeric data types float and real are used for representing floating-point numbers with varying precision. float can store larger numbers than real and can have either 4 or 8 bytes of storage. real uses 4 bytes for storage.

Date and Time

Data TypeDescriptionStorage
dateDate without time3 bytes
datetimeoffsetDate and time with time zone offset8-10 bytes
datetime2Date and time6-8 bytes
smalldatetimeDate and time with less precision4 bytes
datetimeDate and time8 bytes
timeTime without date3-5 bytes

The date and time data types in SQL Server allow the storage and manipulation of date and time information. Each data type has its own characteristics, such as precision and storage size, catering to different use cases.

Binary Strings

Data TypeDescriptionStorage
binaryFixed-width binary stringDefined by data (up to 8,000 bytes)
varbinaryVariable-width binary stringLength of data (up to 8,000 bytes)
imageVariable-width binary string (large)2GB of binary data

Binary string data types in SQL Server store binary data. binary and varbinary can store fixed or variable-width binary data, respectively. The image data type is used for storing large amounts of binary data.

Other Data Types

Data TypeDescriptionStorage
cursorReference to a cursor used for database operations4 bytes
rowversionAutomatically updated binary value for versioning8 bytes
hierarchyidRepresents position in a hierarchy8 bytes
uniqueidentifierGlobally unique identifier (GUID)16 bytes
sql_variantStores values of different data types, except text, ntext, and timestampVaries
xmlStores XML formatted dataUp to 2GB
Spatial Geometry TypesGeometric shapes and spatial data (e.g., Point, LineString)Varies
Spatial Geography TypesGeographic shapes and spatial data (e.g., GeographyPoint)Varies
tableStores a result-set for later processingVaries (depending on data stored)

Other data types in SQL Server cover a range of specialized purposes. cursor is a reference to a cursor used for database operations. rowversion is a binary value for versioning, automatically updated. hierarchyid represents a position in a hierarchy. uniqueidentifier is a globally unique identifier (GUID). sql_variant stores values of different data types. xml is used for storing XML formatted data. Spatial Geometry and Geography Types are used for representing geometric and geographic shapes, respectively. table is used to store a result-set for later processing.

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