SELECTEER tbl_port_config.*, (SELECTEER TOP 1 error_counter1 VANUIT tbl_port_errors WHERE switch_id =tbl_port_config.switch_id) als error_counter_1 WHERE ......
SELECTEER tbl_port_config.*, (SELECTEER TOP 1 error_counter1 VANUIT tbl_port_errors WHERE switch_id =tbl_port_config.switch_id) als error_counter_1 WHERE ......