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    1. General Information
    2. MySQL Installation
    3. Tutorial Introduction
    4. Database Administration
    5. MySQL Optimisation
    6. MySQL Language Reference
    7. MySQL Table Types
    8. MySQL APIs
    9. Extending MySQL
    Chapter 8:  MySQL APIs 585 if (mysql_query(&mysql,query_string)) { // error } else // query succeeded, process any data returned by it { result = mysql_store_result(&mysql); if (result)   // there are rows { num_fields = mysql_num_fields(result); // retrieve rows, then call mysql_free_result(result) } else   // mysql_store_result() returned nothing; should it have? { if (mysql_errno(&mysql)) { fprintf(stderr, "Error: %s\n", mysql_error(&mysql)); } else if (mysql_field_count(&mysql) == 0) { // query does not return data // (it was not a SELECT) num_rows = mysql_affected_rows(&mysql); } } } An alternative (if you know that your query should have returned a result set) is to replace the mysql_errno(&mysql) call with a check if mysql_field_count(&mysql) is = 0.  This will only happen if something went wrong. 8.4.3.37  mysql_num_rows() my_ulonglong mysql_num_rows(MYSQL_RES *result) Description Returns the number of rows in the result set. The  use  of  mysql_num_rows()  depends  on  whether  you  use  mysql_store_result()  or mysql_use_result()  to return the result set.  If you use  mysql_store_result(),  mysql_ num_rows()  may  be  called  immediately.    If  you  use  mysql_use_result(),  mysql_num_ rows()  will  not  return  the  correct  value  until  all  the  rows  in  the  result  set  have  been retrieved. Return Values The number of rows in the result set.
     

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