I have system as below:When I click the 'start' button, the time when I clicked it will be saved in database. And also when I click the 'stop' button.I used this syntax to insert to database:$query = "INSERT INTO down_his VALUES('','$id_machine','$machine_name','$machine_status',now())";I want to make this information in one row. Is it posibble?So when I click the 'start' button, It will just store the information about the time when it start, but the 'stop' column will be blank. And when I click the 'stop' button, it will be completing the first data. Not separately in 2 rows, just like my table now.