JetGetColumnInfo Function

Artikkel
08/26/2021

Applies to: Windows | Windows Server

JetGetColumnInfo Function

The JetGetColumnInfo function retrieves information about a column.

    JET_ERR JET_API JetGetColumnInfo(
      __in          JET_SESID sesid,
      __in          JET_DBID dbid,
      __in          const tchar* szTableName,
      __in          const tchar* szColumnName,
      __out         void* pvResult,
      __in          unsigned long cbMax,
      __in          unsigned long InfoLevel
    );

Parameters

sesid

The database session context to use for the API call.

dbid

Identifies, along with szTableName, the table that contains the column from which the information is retrieved.

szTableName

Identifies, along with dbid, the table that contains the column from which the information is retrieved.

szColumnName

The name of the column that information is fetched for.

pvResult

Pointer to a buffer that will receive the information. The type of the buffer is dependent on InfoLevel. The caller must be configured to align the buffer appropriately.

cbMax

The size, in bytes, of the buffer that is passed in pvResult.

InfoLevel

The type of information to retrieve for the column that is specified by szColumnName. The format of the data stored in pvResult is dependent on this parameter. For the schema of the temporary table, see JET_COLUMNLIST.

These InfoLevels are differentiated by:

JET_ColInfoListSortColumnid will sort the temporary table by columnid.
JET_ColInfoListCompact will compact the output. For more information about the compact output, see JET_COLUMNLIST.

The following options are available for use with this parameter.

Value	Meaning
JET_ColInfo	JET_ColInfo and JET_ColInfoByColid both retrieve the same information. pvResult is interpreted as a JET_COLUMNDEF, and the fields of the JET_COLUMNDEF structure are filled in appropriately.
JET_ColInfoBase	pvResult is interpreted as a JET_COLUMNBASE structure. This is similar to a JET_COLUMNDEF structure. If this function succeeds, the structure is populated with appropriate values. If this function fails, the structure contains undefined data.
JET_ColInfoByColid	Like JET_ColInfo, pvResult is interpreted as a JET_COLUMNDEF, except this InfoLevel indicates that the requested column (szColumName) is not the string column name, but a pointer to a JET_COLUMNID.
JET_ColInfoList	pvResult is interpreted as a JET_COLUMNLIST structure. If this function succeeds, the structure is populated with appropriate values. A temporary table is opened and is identified by the tableid member of the JET_COLUMNLIST structure. The table must be closed with JetCloseTable. If this function fails, the structure contains undefined data.
JET_ColInfoListCompact	Same as JET_ColInfoList.
JET_ColInfoListSortColumnid	Same as JET_ColInfoList; however the resulting table is sorted by columnid, instead of column name.
JET_ColInfoSysTabCursor	JET_ColInfoSysTabCursor is deprecated, and use of it will return JET_errFeatureNotAvailable.
JET_ColInfoBaseByColId	Like JET_ColInfoBase, pvResult is interpreted as a JET_COLUMNBASE, except this InfoLevel indicates that requested column (szColumName) is not the string column name, but a pointer to a JET_COLUMNID. Windows Vista: This value is introduced in Windows Vista.
JET_ColInfoGrbitNonDerivedColumnsOnly	Only return non-derived columns (if the table is derived from a template). This value can be logically or'd into the InfoLevel, when the base InfoLevel is JET_ColInfoList. Windows Vista: This value is introduced Windows Vista.
JET_ColInfoGrbitMinimalInfo	Only return the column name and columnid of each column. This value can be logically or'd into the InfoLevel, when the base InfoLevel is JET_ColInfoList. Windows Vista: This value is introduced in Windows Vista.
JET_ColInfoGrbitSortByColumnid	Sort returned column list by columnid (default is to sort list by column name). This value can be logically or'd into the InfoLevel, when the base InfoLevel is JET_ColInfoList. Windows Vista: This value is introduced in Windows Vista.

Return Value

This function returns the JET_ERR datatype with one of the following return codes. For more information about the possible ESE errors, see Extensible Storage Engine Errors and Error Handling Parameters.

Return code	Description
JET_errSuccess	The operation completed successfully.
JET_errColumnNotFound	The column named szColumnName was not found in the table.
JET_errFeatureNotAvailable	A bad InfoLevel was specified.
JET_errInvalidName	This error can be returned if: A bad name for szTableName was given. A bad name for szColumnName was given.
JET_errInvalidParameter	This error can be returned if: A bad InfoLevel was specified. A NULL szTableName was passed in. The buffer is too small.

Remarks

JetGetTableColumnInfo and JetGetColumnInfo both retrieve information about a column. The difference between them is how the table is identified:

JetGetTableColumnInfo identifies a table by tableid.
JetGetColumnInfo identifies a table by dbid and szTableName combination.

When retrieving data with JET_ColInfoList, JET_ColInfoListSortColumnid, or JET_ColInfoListCompact, a temporary table will be opened. The temporary table contains data, and the JET_COLUMNLIST structure contains sufficient information to traverse the temporary table. The temporary table must be closed with JetCloseTable.

Requirements

Requirement	Value
Client	Requires Windows Vista, Windows XP, or Windows 2000 Professional.
Server	Requires Windows Server 2008, Windows Server 2003, or Windows 2000 Server.
Header	Declared in Esent.h.
Library	Use ESENT.lib.
DLL	Requires ESENT.dll.
Unicode	Implemented as JetGetColumnInfoW (Unicode) and JetGetColumnInfoA (ANSI).

Del via

JetGetColumnInfo Function