Upravit

Sdílet prostřednictvím

SQLMoreResults Function

  • Článek

Conformance
Version Introduced: ODBC 1.0 Standards Compliance: ODBC

Summary
SQLMoreResults determines whether more results are available on a statement containing SELECT, UPDATE, INSERT, or DELETE statements and, if so, initializes processing for those results.

Syntax

  
SQLRETURN SQLMoreResults(  
     SQLHSTMT     StatementHandle);

Arguments

StatementHandle
[Input] Statement handle.

Returns

SQL_SUCCESS, SQL_SUCCESS_WITH_INFO, SQL_STILL_EXECUTING, SQL_NO_DATA, SQL_ERROR, SQL_INVALID_HANDLE, OR SQL_PARAM_DATA_AVAILABLE.

Diagnostics

When SQLMoreResults 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 SQLMoreResults 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.)
01S02 Option value has changed The value of a statement attribute changed as the batch was being processed. (Function returns SQL_SUCCESS_WITH_INFO.)
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.
40001 Serialization failure The transaction was rolled back due to a resource deadlock with another transaction.
40003 Statement completion unknown The associated connection failed during the execution of this function and the state of the transaction cannot be determined.
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 memory required to support execution or completion of the function.
HY008 Operation canceled Asynchronous processing was enabled for the StatementHandle. The SQLMoreResults function was called and, before it completed execution, SQLCancel or SQLCancelHandle was called on the StatementHandle. Then the SQLMoreResults function was called again on the StatementHandle.

The SQLMoreResults function was called and, before it completed execution, SQLCancel or SQLCancelHandle was called on the StatementHandle from a different thread in a multithread application.
HY010 Function sequence error (DM) An asynchronously executing function was called for the connection handle that is associated with the StatementHandle. This asynchronous function was still executing when the SQLMoreResults function was called.

(DM) An asynchronously executing function (not this one) was called for the StatementHandle and was still executing when this function was called.

(DM) SQLExecute, SQLExecDirect, SQLBulkOperations, or SQLSetPos was called for the StatementHandle and returned SQL_NEED_DATA. This function was called before data was sent for all data-at-execution parameters or columns.
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.
HY117 Connection is suspended due to unknown transaction state. Only disconnect and read-only functions are allowed. (DM) For more information about 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 StatementHandle does not support the function.
IM017 Polling is disabled in asynchronous notification mode Whenever the notification model is used, polling is disabled.
IM018 SQLCompleteAsync has not been called to complete the previous asynchronous operation on this handle. If the previous function call on the handle returns SQL_STILL_EXECUTING and if notification mode is enabled, SQLCompleteAsync must be called on the handle to do post-processing and complete the operation.

Comments

SELECT statements return result sets. UPDATE, INSERT, and DELETE statements return a count of affected rows. If any of these statements are batched, submitted with arrays of parameters (numbered in increasing parameter order, in the order that they appear in the batch), or in procedures, they can return multiple result sets or row counts. For information about batches of statements and arrays of parameters, see Batches of SQL Statements and Arrays of Parameter Values.

After executing the batch, the application is positioned on the first result set. The application can call SQLBindCol, SQLBulkOperations, SQLFetch, SQLGetData, SQLFetchScroll, SQLSetPos, and all the metadata functions, on the first or any subsequent result sets, just as it would if there were just a single result set. Once it is done with the first result set, the application calls SQLMoreResults to move to the next result set. If another result set or count is available, SQLMoreResults returns SQL_SUCCESS and initializes the result set or count for additional processing. If any row count-generating statements appear in between result set-generating statements, they can be stepped over by calling SQLMoreResults.After calling SQLMoreResults for UPDATE, INSERT, or DELETE statements, an application can call SQLRowCount.

If there was a current result set with unfetched rows, SQLMoreResults discards that result set and makes the next result set or count available. If all results have been processed, SQLMoreResults returns SQL_NO_DATA. For some drivers, output parameters and return values are not available until all result sets and row counts have been processed. For such drivers, output parameters and return values become available when SQLMoreResults returns SQL_NO_DATA.

Any bindings that were established for the previous result set still remain valid. If the column structures are different for this result set, then calling SQLFetch or SQLFetchScroll may result in an error or truncation. To prevent this, the application has to call SQLBindCol to explicitly rebind as appropriate (or do so by setting descriptor fields). Alternatively, the application can call SQLFreeStmt with an Option of SQL_UNBIND to unbind all the column buffers.

The values of statement attributes, such as cursor type, cursor concurrency, keyset size, or maximum length, may change as the application navigates through the batch by calls to SQLMoreResults. If this happens, SQLMoreResults will return SQL_SUCCESS_WITH_INFO and SQLSTATE 01S02 (Option value has changed).

Calling SQLCloseCursor, or SQLFreeStmt with an Option of SQL_CLOSE, discards all the result sets and row counts that were available as a result of the execution of the batch. The statement handle returns to either the allocated or prepared state. Calling SQLCancel to cancel an asynchronously executing function when a batch has been executed and the statement handle is in the executed, cursor-positioned, or asynchronous state results in all the results sets and row counts generated by the batch being discarded if the cancel call was successful. The statement then returns to the prepared or allocated state.

If a batch of statements or a procedure mixes other SQL statements with SELECT, UPDATE, INSERT, and DELETE statements, these other statements do not affect SQLMoreResults.

For more information, see Multiple Results.

If a searched update, insert, or delete statement in a batch of statements does not affect any rows at the data source, SQLMoreResults returns SQL_SUCCESS. This is different from the case of a searched update, insert, or delete statement that is executed through SQLExecDirect, SQLExecute, or SQLParamData, which returns SQL_NO_DATA if it does not affect any rows at the data source. If an application calls SQLRowCount to retrieve the row count after a call to SQLMoreResults has not affected any rows, SQLRowCount will return SQL_NO_DATA.

For additional information about the valid sequencing of result-processing functions, see Appendix B: ODBC State Transition Tables.

For more information about SQL_PARAM_DATA_AVAILABLE and streamed output parameters, see Retrieving Output Parameters Using SQLGetData.

Availability of Row Counts

When a batch contains multiple consecutive row count-generating statements, it is possible that these row counts are rolled up into just one row count. For example, if a batch has five insert statements, then certain data sources are capable of returning five individual row counts. Certain other data sources return only one row count that represents the sum of the five individual row counts.

When a batch contains a combination of result set-generating and row count-generating statements, row counts may or may not be available at all. The behavior of the driver with respect to the availability of row counts is enumerated in the SQL_BATCH_ROW_COUNT information type available through a call to SQLGetInfo. For example, suppose that the batch contains a SELECT, followed by two INSERTs and another SELECT. Then the following cases are possible:

  • The row counts corresponding to the two INSERT statements are not available at all. The first call to SQLMoreResults will position you on the result set of the second SELECT statement.

  • The row counts corresponding to the two INSERT statements are available individually. (A call to SQLGetInfo does not return the SQL_BRC_ROLLED_UP bit for the SQL_BATCH_ROW_COUNT information type.) The first call to SQLMoreResults will position you on the row count of the first INSERT, and the second call will position you on the row count of the second INSERT. The third call to SQLMoreResults will position you on the result set of the second SELECT statement.

  • The row counts corresponding to the two INSERTs are rolled up into one single row count that is available. (A call to SQLGetInfo returns the SQL_BRC_ROLLED_UP bit for the SQL_BATCH_ROW_COUNT information type.) The first call to SQLMoreResults will position you on the rolled-up row count, and the second call to SQLMoreResults will position you on the result set of the second SELECT.

Certain drivers make row counts available only for explicit batches and not for stored procedures.

For information about See
Canceling statement processing SQLCancel Function
Fetching a block of data or scrolling through a result set SQLFetchScroll Function
Fetching a single row or a block of data in a forward-only direction SQLFetch Function
Fetching part or all of a column of data SQLGetData Function

See Also

ODBC API Reference
ODBC Header Files
Retrieving Output Parameters Using SQLGetData