const char * mysql_stmt_error(MYSQL_STMT * stmt);
stmt- a statement handle, which was previously allocated by mysql_stmt_init().
Returns a string containing the error message for the most recently invoked statement function that can succeed or fail. The string will be empty if no error occurred.
Client error messages are listed in the errmsg.h header file, server error messages are listed in the mysqld_error.h header file of the server source distribution.