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Data types (Transact-SQL)

  • Článek

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) Warehouse in Microsoft Fabric

In the SQL Server Database Engine, each column, local variable, expression, and parameter has a related data type. A data type is an attribute that specifies the type of data that the object can hold: integer data, character data, monetary data, date and time data, binary strings, and so on.

SQL Server supplies a set of system data types that define all the types of data that can be used with SQL Server. You can also define your own data types in Transact-SQL or the Microsoft .NET Framework. Alias data types are based on the system-supplied data types. For more information about alias data types, see CREATE TYPE. User-defined types obtain their characteristics from the methods and operators of a class that you create by using one of the programming languages supported by the .NET Framework.

When two expressions combined by an operator have different data types, collations, precision, scale, or length, the characteristics of the result are determined by the following conditions:

  • The data type of the result is determined by applying the rules of data type precedence to the data types of the input expressions.

  • The collation of the result is determined by the rules of collation precedence when the result data type is char, varchar, text, nchar, nvarchar, or ntext. For more information, see Collation precedence.

  • The precision, scale, and length of the result depend on the precision, scale, and length of the input expressions. For more information, see Precision, scale, and length (Transact-SQL).

SQL Server provides data type synonyms for ISO compatibility. For more information, see Data type synonyms.

For more specific information on data types in Azure Synapse Analytics, see Table data types in Synapse SQL.

For more specific information on data types in Microsoft Fabric, see Data type.

Data type categories

Data types in SQL Server are organized into the following categories:

In SQL Server, based on their storage characteristics, some data types are designated as belonging to the following groups:

  • Large value data types: varchar(max), and nvarchar(max)

  • Large object data types: text, ntext, image, varbinary(max), and xml

    Note

    sp_help returns -1 as the length for the large-value and xml data types.

Exact numerics

1 The bit data type is used for storing Boolean values.

2 The decimal and numeric data types are identical.

Approximate numerics

Date and time

Character strings

Unicode character strings

Binary strings

Other data types

1 The geography and geometry data types are spatial types.

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