How to query in a friend's table and own the same friends and not own friends of the user

How to query in a friend table and own users who have the same friends and are not their own friends


The UID and the friend ID are all in the other table.
How to query in a friend table and own users who have the same friends and are not their own friends

------Solution--------------------
There are at least two fields in Friends table friend, user_id fields and friend_id fields
1. First find out your friends: select friend_id from friend where user_id = "Zhangshan";
2.select distinct user_id from friend where friend_id in (select friend_id from friend where user_id = "Zhangshan") and US er_id! = "Zhangshan" and user_id not in (select friend_id from friend where user_id = "Zhangshan");

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