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25.2.9. C API Handling of Multiple Query Execution

MySQL 5.1 supports the execution of multiple statements specified in a single query string. To use this capability with a given connection, you must specify the CLIENT_MULTI_STATEMENTS option in the flags parameter to mysql_real_connect() when opening the connection. You can also set this for an existing connection by calling mysql_set_server_option(MYSQL_OPTION_MULTI_STATEMENTS_ON).

By default, mysql_query() and mysql_real_query() return only the first query status and the subsequent queries status can be processed using mysql_more_results() and mysql_next_result().

/* Connect to server with option CLIENT_MULTI_STATEMENTS */
mysql_real_connect(..., CLIENT_MULTI_STATEMENTS);

/* Now execute multiple queries */
mysql_query(mysql,"DROP TABLE IF EXISTS test_table;\
                   CREATE TABLE test_table(id INT);\
                   INSERT INTO test_table VALUES(10);\
                   UPDATE test_table SET id=20 WHERE id=10;\
                   SELECT * FROM test_table;\
                   DROP TABLE test_table");
do
{
  /* Process all results */
  ...
  printf("total affected rows: %lld", mysql_affected_rows(mysql));
  ...
  if (!(result= mysql_store_result(mysql)))
  {
     printf(stderr, "Got fatal error processing query\n");
     exit(1);
  }
  process_result_set(result); /* client function */
  mysql_free_result(result);
} while (!mysql_next_result(mysql));

The multiple-statement capability can be used with mysql_query() or mysql_real_query(). It cannot be used with the prepared statement interface. Prepared statement handles are defined to work only with strings that contain a single statement.


 
 
  Published under the terms of the GNU General Public License Design by Interspire