I have a users table and lastlogin table. How can I update the last login table with the information from users table. I tried

UPDATE lastlogin SET time = NOW() WHERE ?

I don't know what to write after the WHERE clause since the lastlogin table has only two fields( lastlogin_id and lastlogintime).

The users table has nothing related to the lastlogin table.

If I tried this UPDATE lastlogin SET lastlogintime = NOW() WHERE(SELECT username FROM users WHERE username = $sessionuser);

That means it will keep udating the lastlogin table anytime a different user log in.

How can I keep the last login time of each user?