在MySQL中，如何使用一个表中的信息来更新另一个表

Question

I have two tables: teams, and persons.

table teams have three columns, id , name , leader

table persons have these columns: hash , team_id

teams.leader is a MD5 hash that must match persons.hash in order to determine which person is leader of a given team.

I need to run a query on MySQL that does the following:

1) Retrieve all the leaders of a team, and the team id:

SELECT `id`,`leader` FROM `teams`;

2) Use such information to update team_id on table persons

This is my current Query: SELECT id FROM teams INNER JOIN persons ON teams . leader = persons . hash

but I haven't been able to come up with a solution that allows me update column team_id with the corresponding leader. I've been thinking probably using cursors, but not sure about it. Any ideas?

Answer 1

You can use the multiple table UPDATE syntax to join the tables:

UPDATE teams JOIN persons ON teams.leader = persons.hash
SET persons.team_id = teams.id