5.4.51 mysql_next_result()

int
mysql_next_result(MYSQL *mysql)

Description

Note

mysql_next_result() is a synchronous function. Its asynchronous counterpart is mysql_next_result_nonblocking(), for use by applications that require asynchronous communication with the server. See Chapter 7, C API Asynchronous Interface.

mysql_next_result() is used when you execute multiple statements specified as a single statement string, or when you use CALL statements to execute stored procedures, which can return multiple result sets.

mysql_next_result() reads the next statement result and returns a status to indicate whether more results exist. If mysql_next_result() returns an error, there are no more results.

Before each call to mysql_next_result(), you must call mysql_free_result() for the current statement if it is a statement that returned a result set (rather than just a result status).

After calling mysql_next_result() the state of the connection is as if you had called mysql_real_query() or mysql_query() for the next statement. This means that you can call mysql_store_result(), mysql_warning_count(), mysql_affected_rows(), and so forth.

If your program uses CALL statements to execute stored procedures, the CLIENT_MULTI_RESULTS flag must be enabled. This is because each CALL returns a result to indicate the call status, in addition to any result sets that might be returned by statements executed within the procedure. Because CALL can return multiple results, process them using a loop that calls mysql_next_result() to determine whether there are more results.

CLIENT_MULTI_RESULTS can be enabled when you call mysql_real_connect(), either explicitly by passing the CLIENT_MULTI_RESULTS flag itself, or implicitly by passing CLIENT_MULTI_STATEMENTS (which also enables CLIENT_MULTI_RESULTS). CLIENT_MULTI_RESULTS is enabled by default.

It is also possible to test whether there are more results by calling mysql_more_results(). However, this function does not change the connection state, so if it returns true, you must still call mysql_next_result() to advance to the next result.

For an example that shows how to use mysql_next_result(), see Section 3.6.3, “Multiple Statement Execution Support”.

Return Values

Return Value	Description
0	Successful and there are more results
-1	Successful and there are no more results
>0	An error occurred

Errors

• CR_COMMANDS_OUT_OF_SYNC

  Commands were executed in an improper order. For example, if you did not call mysql_use_result() for a previous result set.

• CR_SERVER_GONE_ERROR

  The MySQL server has gone away.

• CR_SERVER_LOST

  The connection to the server was lost during the query.

• CR_UNKNOWN_ERROR

  An unknown error occurred.