SELECT tbl_port_config。*、(SELECT TOP 1 error_counter1 FROM tbl_port_errors WHERE switch_id =tbl_port_config.switch_id)as error_counter_1 WHERE ......
SELECT tbl_port_config。*、(SELECT TOP 1 error_counter1 FROM tbl_port_errors WHERE switch_id =tbl_port_config.switch_id)as error_counter_1 WHERE ......