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SQLGetDescField Function

  • Article

Conformance
Version Introduced: ODBC 3.0 Standards Compliance: ISO 92

Summary
SQLGetDescField returns the current setting or value of a single field of a descriptor record.

Syntax

  
SQLRETURN SQLGetDescField(  
     SQLHDESC        DescriptorHandle,  
     SQLSMALLINT     RecNumber,  
     SQLSMALLINT     FieldIdentifier,  
     SQLPOINTER      ValuePtr,  
     SQLINTEGER      BufferLength,  
     SQLINTEGER *    StringLengthPtr);

Arguments

DescriptorHandle
[Input] Descriptor handle.

RecNumber
[Input] Indicates the descriptor record from which the application seeks information. Descriptor records are numbered from 0, with record number 0 being the bookmark record. If the FieldIdentifier argument indicates a header field, RecNumber is ignored. If RecNumber is less than or equal to SQL_DESC_COUNT but the row does not contain data for a column or parameter, a call to SQLGetDescField will return the default values of the fields. (For more information, see "Initialization of Descriptor Fields" in SQLSetDescField.)

FieldIdentifier
[Input] Indicates the field of the descriptor whose value is to be returned. For more information, see the "FieldIdentifier Argument" section in SQLSetDescField.

ValuePtr
[Output] Pointer to a buffer in which to return the descriptor information. The data type depends on the value of FieldIdentifier.

If ValuePtr is integer type, applications should use a buffer of SQLULEN and initialize the value to 0 before calling this function as some drivers may only write the lower 32-bit or 16-bit of a buffer and leave the higher-order bit unchanged.

If ValuePtr is NULL, StringLengthPtr will still return the total number of bytes (excluding the null-termination character for character data) available to return in the buffer pointed to by ValuePtr.

BufferLength
[Input] If FieldIdentifier is an ODBC-defined field and ValuePtr points to a character string or a binary buffer, this argument should be the length of *ValuePtr. If FieldIdentifier is an ODBC-defined field and *ValuePtr is an integer, BufferLength is ignored. If the value in *ValuePtr is of a Unicode data type (when calling SQLGetDescFieldW), the BufferLength argument must be an even number.

If FieldIdentifier is a driver-defined field, the application indicates the nature of the field to the Driver Manager by setting the BufferLength argument. BufferLength can have the following values:

  • If *ValuePtr is a pointer to a character string, then BufferLength is the length of the string or SQL_NTS.

  • If *ValuePtr is a pointer to a binary buffer, then the application places the result of the SQL_LEN_BINARY_ATTR(length) macro in BufferLength. This places a negative value in BufferLength.

  • If *ValuePtr is a pointer to a value other than a character string or binary string, then BufferLength should have the value SQL_IS_POINTER.

  • If *ValuePtr is contains a fixed-length data type, then BufferLength is either SQL_IS_INTEGER, SQL_IS_UINTEGER, SQL_IS_SMALLINT, or SQL_IS_USMALLINT, as appropriate.

StringLengthPtr
[Output] Pointer to the buffer in which to return the total number of bytes (excluding the number of bytes required for the null-termination character) available to return in *ValuePtr.

Returns

SQL_SUCCESS, SQL_SUCCESS_WITH_INFO, SQL_ERROR, SQL_NO_DATA, or SQL_INVALID_HANDLE.

SQL_NO_DATA is returned if RecNumber is greater than the current number of descriptor records.

SQL_NO_DATA is returned if DescriptorHandle is an IRD handle and the statement is in the prepared or executed state but there was no open cursor associated with it.

Diagnostics

When SQLGetDescField returns SQL_ERROR or SQL_SUCCESS_WITH_INFO, an associated SQLSTATE value can be obtained by calling SQLGetDiagRec with a HandleType of SQL_HANDLE_STMT and a Handle of StatementHandle. The following table lists the SQLSTATE values commonly returned by SQLGetDescField and explains each one in the context of this function; the notation "(DM)" precedes the descriptions of SQLSTATEs returned by the Driver Manager. The return code associated with each SQLSTATE value is SQL_ERROR, unless noted otherwise.

SQLSTATE Error Description
01000 General warning Driver-specific informational message. (Function returns SQL_SUCCESS_WITH_INFO.)
01004 String data, right truncated The buffer *ValuePtr was not large enough to return the entire descriptor field, so the field was truncated. The length of the untruncated descriptor field is returned in *StringLengthPtr. (Function returns SQL_SUCCESS_WITH_INFO.)
07009 Invalid descriptor index (DM) The RecNumber argument was equal to 0, the SQL_ATTR_USE_BOOKMARK statement attribute was SQL_UB_OFF, and the DescriptorHandle argument was an IRD handle. (This error can be returned for an explicitly allocated descriptor only if the descriptor is associated with a statement handle.)

The FieldIdentifier argument was a record field, the RecNumber argument was 0, and the DescriptorHandle argument was an IPD handle.

The RecNumber argument was less than 0.
08S01 Communication link failure The communication link between the driver and the data source to which the driver was connected failed before the function completed processing.
HY000 General error An error occurred for which there was no specific SQLSTATE and for which no implementation-specific SQLSTATE was defined. The error message returned by SQLGetDiagRec in the *MessageText buffer describes the error and its cause.
HY001 Memory allocation error The driver was unable to allocate the memory required to support execution or completion of the function.
HY007 Associated statement is not prepared DescriptorHandle was associated with a StatementHandle as an IRD, and the associated statement handle had not been prepared or executed.
HY010 Function sequence error (DM) DescriptorHandle was associated with a StatementHandle for which an asynchronously executing function (not this one) was called and was still executing when this function was called.

(DM) DescriptorHandle was associated with a StatementHandle for which SQLExecute, SQLExecDirect, SQLBulkOperations, or SQLSetPos was called and returned SQL_NEED_DATA. This function was called before data was sent for all data-at-execution parameters or columns.

(DM) An asynchronously executing function was called for the connection handle that is associated with the DescriptorHandle. This asynchronous function was still executing when the SQLGetDescField function was called.
HY013 Memory management error The function call could not be processed because the underlying memory objects could not be accessed, possibly because of low memory conditions.
HY021 Inconsistent descriptor information The SQL_DESC_TYPE and SQL_DESC_DATETIME_INTERVAL_CODE fields do not form a valid ODBC SQL type, a valid driver-specific SQL type (for IPDs), or a valid ODBC C type (for APDs or ARDs).
HY090 Invalid string or buffer length (DM) *ValuePtr was a character string, and BufferLength was less than zero.
HY091 Invalid descriptor field identifier FieldIdentifier was not an ODBC-defined field and was not an implementation-defined value.

FieldIdentifier was undefined for the DescriptorHandle.
HY117 Connection is suspended due to unknown transaction state. Only disconnect and read-only functions are allowed. (DM) For more information about the suspended state, see SQLEndTran Function.
HYT01 Connection timeout expired The connection timeout period expired before the data source responded to the request. The connection timeout period is set through SQLSetConnectAttr, SQL_ATTR_CONNECTION_TIMEOUT.
IM001 Driver does not support this function (DM) The driver associated with the DescriptorHandle does not support the function.

Comments

An application can call SQLGetDescField to return the value of a single field of a descriptor record. A call to SQLGetDescField can return the setting of any field in any descriptor type, including header fields, record fields, and bookmark fields. An application can obtain the settings of multiple fields in the same or different descriptors, in arbitrary order, by making repeated calls to SQLGetDescField. SQLGetDescField can also be called to return driver-defined descriptor fields.

For performance reasons, an application should not call SQLGetDescField for an IRD before executing a statement.

The settings of multiple fields that describe the name, data type, and storage of column or parameter data can also be retrieved in a single call to SQLGetDescRec. SQLGetStmtAttr can be called to return the setting of a single field in the descriptor header that is also a statement attribute. SQLColAttribute, SQLDescribeCol, and SQLDescribeParam return record or bookmark fields.

When an application calls SQLGetDescField to retrieve the value of a field that is undefined for a particular descriptor type, the function returns SQL_SUCCESS but the value returned for the field is undefined. For example, calling SQLGetDescField for the SQL_DESC_NAME or SQL_DESC_NULLABLE field of an APD or ARD will return SQL_SUCCESS but an undefined value for the field.

When an application calls SQLGetDescField to retrieve the value of a field that is defined for a particular descriptor type but that has no default value and has not been set yet, the function returns SQL_SUCCESS but the value returned for the field is undefined. For more information on the initialization of descriptor fields and descriptions of the fields, see "Initialization of Descriptor Fields" in SQLSetDescField. For more information on descriptors, see Descriptors.

For information about See
Getting multiple descriptor fields SQLGetDescRec Function
Setting a single descriptor field SQLSetDescField Function
Setting multiple descriptor fields SQLSetDescRec Function

See Also

ODBC API Reference
ODBC Header Files