如何使用提交按钮将用户标识添加到另一个表

Question

I am creating a site that allows users to view desired 'teams' and can then join them with the click of one button.

I have my users table which contains: user_id, user_name, team_id

Then, I have my teams table which contains: team_id, team_name, team_players

How would I go about having the users to join a group, each user can also only be in 1 team at a time.

Answer 1

You should start by adding the team_id field to the users table as a foreign key and allow it to be NULL.

Then you would display the team names in an html form with a radio button for each team.

In a PHP file (which should be set to the action of your form) create an if statement based on the values you assigned to each radio button. In each if block, execute a sql UPDATE statement that will add the appropriate group_ID to the right user instance.

Answer 2

If you want each user to be able to join multiple teams, and each team to have multiple users, then you need a "join table."

Table teams_users would contain team_id , user_id . You can make a composite primary key on team_id, user_id (preventing a user from joining the same team twice).

Then you can get a team with:

SELECT * FROM users t1 right join teams_users t2 ON t1.team_id = t2.team_id WHERE t2.team_name = 'the rascals'

Even if you only want players to join one team at a time, you might still want to use the join table in case you ever change your mind. It would be very easy. To only allow one team per user, put a unique constraint on user_id in the join table. If you later decide you want to allow multiple teams, you just remove that constraint.

If a user tries the "join team" action, you simply check for the user_id's existence in the join table.

SELECT * FROM teams_users WHERE user_id = $user_id

If it does exist, you retrieve its matching team_id and tell them, "sorry, you are already in team 'the rascals'. You must leave that team if you want to join another." If they drop their team, you simply do:

DELETE from teams_users WHERE user_id = 5

If they add a team, you just do:

INSERT INTO teams_users ($team_id, $user_id) #// (assuming PHP variables).

The INSERT query will only work if they are not already in a team. If they are you would get an error message. You could also look at "INSERT ON DUPLICATE KEY UPDATE ..." queries. But I would advise against that because you want to warn users before they change teams.