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Date and Time Data in SQL Server 2008 (ADO.NET)

  • Artykuł

SQL Server 2008 introduces new data types for handling date and time information. The new data types include separate types for date and time, and expanded data types with greater range, precision, and time-zone awareness. Starting with the .NET Framework version 3.5 Service Pack (SP) 1, the .NET Framework Data Provider for SQL Server (System.Data.SqlClient) provides full support for all the new features of the SQL Server 2008 Database Engine. You must install the .NET Framework 3.5 SP1 (or later) to use these new features with SqlClient.

Versions of SQL Server earlier than SQL Server 2008 only had two data types for working with date and time values: datetime and smalldatetime. Both of these data types contain both the date value and a time value, which makes it difficult to work with only date or only time values. Also, these data types only support dates that occur after the introduction of the Gregorian calendar in England in 1753. Another limitation is that these older data types are not time-zone aware, which makes it difficult to work with data that originates from multiple time zones.

Complete documentation for SQL Server data types is available in SQL Server Books Online. The following table lists the version-specific entry-level topics for date and time data.

SQL Server 2000

SQL Server 2005

SQL Server 2008

datetime and smalldatetime

Using Date and Time Data

Using Date and Time Data

Date/Time Data Types Introduced in SQL Server 2008

The following table describes the new date and time data types.

SQL Server data type

Description

date

The date data type has a range of January 1, 01 through December 31, 9999 with an accuracy of 1 day. The default value is January 1, 1900. The storage size is 3 bytes.

time

The time data type stores time values only, based on a 24-hour clock. The time data type has a range of 00:00:00.0000000 through 23:59:59.9999999 with an accuracy of 100 nanoseconds. The default value is 00:00:00.0000000 (midnight). The time data type supports user-defined fractional second precision, and the storage size varies from 3 to 6 bytes, based on the precision specified.

datetime2

The datetime2 data type combines the range and precision of the date and time data types into a single data type.

The default values and string literal formats are the same as those defined in the date and time data types.

datetimeoffset

The datetimeoffset data type has all the features of datetime2 with an additional time zone offset. The time zone offset is represented as [+|-] HH:MM. HH is 2 digits ranging from 00 to 14 that represent the number of hours in the time zone offset. MM is 2 digits ranging from 00 to 59 that represent the number of additional minutes in the time zone offset. Time formats are supported to 100 nanoseconds. The mandatory + or - sign indicates whether the time zone offset is added or subtracted from UTC (Universal Time Coordinate or Greenwich Mean Time) to obtain the local time.

Note

If the Type System Version is not explicitly set to SQL Server 2008 or Latest in the connection string, datetime values will be processed by using the default SQL Server 2005 type system. For more information about using the Type System Version keywords, see New Features in SQL Server 2008 (ADO.NET).

Date Format and Date Order

How SQL Server parses date and time values depends not only on the type system version and server version, but also on the server's default language and format settings. A date string that works for the date formats of one language might be unrecognizable if the query is executed by a connection that uses a different language and date format setting.

The Transact-SQL SET LANGUAGE statement implicitly sets the DATEFORMAT that determines the order of the date parts. You can use the SET DATEFORMAT Transact-SQL statement on a connection to disambiguate date values by ordering the date parts in MDY, DMY, YMD, YDM, MYD, or DYM order.

If you do not specify any DATEFORMAT for the connection, SQL Server uses the default language associated with the connection. For example, a date string of '01/02/03' would be interpreted as MDY (January 2, 2003) on a server with a language setting of United States English, and as DMY (February 1, 2003) on a server with a language setting of British English. The year is determined by using SQL Server's cutoff year rule, which defines the cutoff date for assigning the century value. For more information, see two digit year cutoff Option in SQL Server Books Online.

Note

The YDM date format is not supported when converting from a string format to date, time, datetime2, or datetimeoffset.

For more information about how SQL Server interprets date and time data, see Using Date and Time Data in SQL Server 2008 Books Online.

Date/Time Data Types and Parameters

You can specify the data type of a SqlParameter by using one of the SqlDbType enumerations. The following enumerations have been added to SqlDbType to support the new date and time data types.

  • SqlDbType.Date

  • SqlDbType.Time

  • SqlDbType.DateTime2

  • SqlDbType.DateTimeOffSet

You can also specify the type of a SqlParameter generically by setting the DbType property of a SqlParameter object to a particular DbType enumeration value. The following enumeration values have been added to DbType to support the datetime2 and datetimeoffset data types:

  • DbType.DateTime2

  • DbType.DateTimeOffset

These new enumerations supplement the Date, Time, and DateTime enumerations, which existed in earlier versions of the .NET Framework.

The .NET Framework data provider type of a parameter object is inferred from the .NET Framework type of the value of the parameter object, or from the DbType of the parameter object. No new System.Data.SqlTypes data types have been introduced to support the new date and time data types. The following table describes the mappings between the SQL Server 2008 date and time data types and the CLR data types.

SQL Server data type

.NET Framework type

System.Data.SqlDbType

System.Data.DbType

date

System.DateTime

Date

Date

time

System.TimeSpan

Time

Time

datetime2

System.DateTime

DateTime2

DateTime2

datetimeoffset

System.DateTimeOffset

DateTimeOffset

DateTimeOffset

datetime

System.DateTime

DateTime

DateTime

smalldatetime

System.DateTime

DateTime

DateTime

SqlParameter Properties

The following table describes SqlParameter properties that are relevant to date and time data types.

Property

Description

IsNullable

Gets or sets whether a value is nullable. When you send a null parameter value to the server, you must specify DBNull, rather than null (Nothing in Visual Basic). For more information about database nulls, see Handling Null Values (ADO.NET).

Precision

Gets or sets the maximum number of digits used to represent the value. This setting is ignored for date and time data types.

Scale

Gets or sets the number of decimal places to which the time portion of the value is resolved for Time, DateTime2, and DateTimeOffset. The default value is 0, which means that the actual scale is inferred from the value and sent to the server.

Size

Ignored for date and time data types.

Value

Gets or sets the parameter value.

SqlValue

Gets or sets the parameter value.

Note

Time values that are less than zero or greater than or equal to 24 hours will throw an ArgumentException.

Creating Parameters

You can create a SqlParameter object by using its constructor, or by adding it to a SqlCommand Parameters collection by calling the Add method of the SqlParameterCollection. The Add method will take as input either constructor arguments or an existing parameter object.

The next sections in this topic provide examples of how to specify date and time parameters. For additional examples of working with parameters, see Configuring Parameters and Parameter Data Types (ADO.NET) and DataAdapter Parameters (ADO.NET).

Date Example

The following code fragment demonstrates how to specify a date parameter.

        SqlParameter parameter = new SqlParameter();
        parameter.ParameterName = "@Date";
        parameter.SqlDbType = SqlDbType.Date;
        parameter.Value = "2007/12/1";

        Dim parameter As New SqlParameter()
        parameter.ParameterName = "@Date"
        parameter.SqlDbType = SqlDbType.Date
        parameter.Value = "2007/12/1"

Time Example

The following code fragment demonstrates how to specify a time parameter.

        SqlParameter parameter = new SqlParameter();
        parameter.ParameterName = "@time";
        parameter.SqlDbType = SqlDbType.Time;
        parameter.Value = DateTime.Parse("23:59:59").TimeOfDay;

        Dim parameter As New SqlParameter()
        parameter.ParameterName = "@Time"
        parameter.SqlDbType = SqlDbType.Time
        parameter.Value = DateTime.Parse("23:59:59").TimeOfDay;

Datetime2 Example

The following code fragment demonstrates how to specify a datetime2 parameter with both the date and time parts.

        SqlParameter parameter = new SqlParameter();
        parameter.ParameterName = "@Datetime2";
        parameter.SqlDbType = SqlDbType.DateTime2;
        parameter.Value = DateTime.Parse("1666-09-02 1:00:00");

        Dim parameter As New SqlParameter()
        parameter.ParameterName = "@Datetime2"
        parameter.SqlDbType = SqlDbType.DateTime2
        parameter.Value = DateTime.Parse("1666-09-02 1:00:00");

DateTimeOffSet Example

The following code fragment demonstrates how to specify a DateTimeOffSet parameter with a date, a time, and a time zone offset of 0.

        SqlParameter parameter = new SqlParameter();
        parameter.ParameterName = "@DateTimeOffSet";
        parameter.SqlDbType = SqlDbType.DateTimeOffSet;
        parameter.Value = DateTimeOffset.Parse("1666-09-02 1:00:00+0");

        Dim parameter As New SqlParameter()
        parameter.ParameterName = "@DateTimeOffSet"
        parameter.SqlDbType = SqlDbType.DateTimeOffSet
        parameter.Value = DateTimeOffset.Parse("1666-09-02 1:00:00+0");

AddWithValue

You can also supply parameters by using the AddWithValue method of a SqlCommand, as shown in the following code fragment. However, the AddWithValue method does not allow you to specify the DbType or SqlDbType for the parameter.

command.Parameters.AddWithValue( 
    "@date", DateTimeOffset.Parse("16660902"));

command.Parameters.AddWithValue( _
    "@date", DateTimeOffset.Parse("16660902"))

The @date parameter could map to a date, datetime, or datetime2 data type on the server. When working with the new datetime data types, you must explicitly set the parameter's SqlDbType property to the data type of the instance. Using Variant or implicitly supplying parameter values can cause problems with backward compatibility with the datetime and smalldatetime data types.

The following table shows which SqlDbTypes are inferred from which CLR types:

CLR type

Inferred SqlDbType

DateTime

SqlDbType.DateTime

TimeSpan

SqlDbType.Time

DateTimeOffset

SqlDbType.DateTimeOffset

Retrieving Date and Time Data

The following table describes methods that are used to retrieve SQL Server 2008 date and time values.

SqlClient method

Description

GetDateTime

Retrieves the specified column value as a DateTime structure.

GetDateTimeOffset

Retrieves the specified column value as a DateTimeOffset structure.

GetProviderSpecificFieldType

Returns the type that is the underlying provider-specific type for the field. Returns the same types as GetFieldType for new date and time types.

GetProviderSpecificValue

Retrieves the value of the specified column. Returns the same types as GetValue for the new date and time types.

GetProviderSpecificValues

Retrieves the values in the specified array.

GetSqlString

Retrieves the column value as a SqlString. An InvalidCastException occurs if the data cannot be expressed as a SqlString.

GetSqlValue

Retrieves column data as its default SqlDbType. Returns the same types as GetValue for the new date and time types.

GetSqlValues

Retrieves the values in the specified array.

GetString

Retrieves the column value as a string if the Type System Version is set to SQL Server 2000 or SQL Server 2005. An InvalidCastException occurs if the data cannot be expressed as a string.

GetTimeSpan

Retrieves the specified column value as a Timespan structure.

GetValue

Retrieves the specified column value as its underlying CLR type.

GetValues

Retrieves column values in an array.

GetSchemaTable

Returns a DataTable that describes the metadata of the result set.

Note

The new date and time SqlDbTypes are not supported for code that is executing in-process in SQL Server. An exception will be raised if one of these types is passed to the server.

Specifying Date and Time Values as Literals

You can specify date and time data types by using a variety of different literal string formats, which SQL Server then evaluates at run time, converting them to internal date/time structures. SQL Server recognizes date and time data that is enclosed in single quotation marks ('). The following examples demonstrate some formats:

  • Alphabetic date formats, such as 'October 15, 2006'.

  • Numeric date formats, such as '10/15/2006'.

  • Unseparated string formats, such as '20061015', which would be interpreted as October 15, 2006 if you are using the ISO standard date format.

Note

You can find complete documentation for all of the literal string formats and other features of the date and time data types in SQL Server Books Online.

Time values that are less than zero or greater than or equal to 24 hours will throw an ArgumentException.

Resources in SQL Server 2008 Books Online

For more information about working with date and time values in SQL Server 2008, see the following resources in SQL Server 2008 Books Online.

Topic

Description

Date and Time Data Types and Functions (Transact-SQL)

Provides an overview of all Transact-SQL date and time data types and functions.

Using Date and Time Data

Provides information about the date and time data types and functions, and examples of using them.

Data Types (Transact-SQL)

Describes system data types in SQL Server 2008.

See Also

Concepts

SQL Server Data Type Mappings (ADO.NET)

Configuring Parameters and Parameter Data Types (ADO.NET)

Other Resources

SQL Server Data Types and ADO.NET

ADO.NET Managed Providers and DataSet Developer Center