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Descriptor Fields for Table-Valued Parameter Constituent Columns

The table-valued parameter descriptor fields described in this section are manipulated by using SQLSetDescField and SQLSetDescField with the handle for the implementation parameter descriptor (IPD).

SQL_DESC_AUTO_UNIQUE_VALUE is used for table-valued parameters as well as other features.

Attribute name

Type

Description

SQL_DESC_AUTO_UNIQUE_VALUE

SQLINTEGER

SQL_TRUE indicates that this column is an identity column.

SQL Server can use this information to optimize performance, but applications are not required to set it for identity columns.

The following attributes are added to all parameter types in the application parameter descriptor (APD) and implementation parameter descriptor (IPD):

Attribute name

Type

Description

SQL_CA_SS_COLUMN_COMPUTED

SQLSMALLINT

SQL_TRUE indicates that this column is computed.

SQL Server can use this information to optimize performance, but applications are not required to set it for computed columns.

This attribute is ignored for bindings that are not table-valued parameter columns.

SQL_CA_SS_COLUMN_IN_UNIQUE_KEY

SQLSMALLINT

SQL_TRUE indicates that a table-valued parameter column participates in a unique key. This can result in better query performance. This attribute is ignored for bindings that are not table-valued parameter columns.

SQL_CA_SS_COLUMN_SORT_ORDER

SQLSMALLINT

Indicates the sort order of a table-valued parameter column. This can result in better query performance. This attribute is ignored for bindings that are not table-valued parameter columns. The possible values are the following:

  • SQL_SS_ASCENDING_ORDER

  • SQL_SS_DESCENDING_ORDER

  • SQL_SS_ORDER_UNSPECIFIED

Values other than SQL_SS_ASCENDING_ORDER and SQL_SS_DESCENDING_ORDER generate an error with SQLSTATE HY024 and message 'Invalid attribute value' and are treated as SQL_SS_ORDER_UNSPECIFIED, which is the default value for this attribute.

SQL_CA_SS_COLUMN_SORT_ORDINAL

SQLSMALLINT

Indicates the ordinal of a table-valued parameter column in the set of columns that define the overall ordering for a table-valued parameter. This can result in better query performance. This attribute is ignored for bindings that are not table-valued parameter columns. Sort ordinals start at 1. A value of 0, the default, indicates that a table-valued parameter column does not have column ordering.

SQL_CA_SS_COLUMN_HAS_DEFAULT_VALUE

SQLSMALLINT

Indicates whether all rows in the table-valued parameter will have the default value for this column. For table-valued parameters, it is not possible to select the default value on a row-by-row basis. A value of SQL_FALSE indicates that rows will have non-default values. This is the default. A value of SQL_TRUE indicates that this column will have default values for all rows.

If set to SQL_TRUE, no data will be sent to the server.

This field can also be used with identity or computed columns if the column values are not required for server processing.

These attributes are only valid for table-valued parameter columns. They are ignored for other parameters.

If SQL_CA_SS_COL_HAS_DEFAULT_VALUE is set for a table-valued parameter column, SQL_DESC_DATA_PTR for that column must be a null pointer. Otherwise, SQLExecute or SQLExecDirect will return SQL_ERROR. A diagnostic record will be generated with SQLSTATE=07S01 and the message "Invalid use of default parameter for parameter <p>, column <c>", where <p> is the parameter ordinal and <c> is the column ordinal.

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