SELECT user.id, friends.this_friend_id, friends.that_friend_id
FROM friends
INNER JOIN user
ON friends.this_friend_id = user.id OR friends.that_friend_id = user.id
WHERE friends.this_friend_id = 3 OR friends.that_friend_id = 3;
The WHERE clause goes after the JOIN clause(s):
SELECT user.id, friends.this_friend_id, friends.that_friend_id
FROM friends
INNER JOIN user
ON friends.this_friend_id = user.id OR friends.that_friend_id = user.id
WHERE friends.this_friend_id = 3 OR friends.that_friend_id = 3;
SELECT user.id, friends.this_friend_id, friends.that_friend_id
FROM friends
INNER JOIN user
ON friends.this_friend_id = user.id
OR friends.that_friend_id = user.id;
WHERE friends.this_friend_id = 3
OR friends.that_friend_id = 3
但是使用或语句并不好，因为它会导致完整的表格扫描 如果您想创建一个更具性能的脚本，则可以在下面使用联合语句而不是or the the_friend_id and that_friend_id加入。
SELECT user.id, friends.this_friend_id, friends.that_friend_id
FROM [friends]
INNER JOIN [user]
ON friends.this_friend_id = user.id
WHERE friends.this_friend_id = 3
union
SELECT user.id, friends.this_friend_id, friends.that_friend_id
FROM [friends]
INNER JOIN [user]
ON friends.that_friend_id = user.id
WHERE friends.that_friend_id = 3
So you've got the order of operators the wrong way around. The operator order of a simple query should be:
SELECT
FROM
JOIN
WHERE
ORDER
So your query would turn into:
SELECT user.id, friends.this_friend_id, friends.that_friend_id
FROM friends
INNER JOIN user
ON friends.this_friend_id = user.id
OR friends.that_friend_id = user.id;
WHERE friends.this_friend_id = 3
OR friends.that_friend_id = 3
However using or statements is not great as it causes full scans of tables. If you wanted to create a more performant script you could do the below, where you use the union statement instead of the or to get this_friend_id and that_friend_id join.
SELECT user.id, friends.this_friend_id, friends.that_friend_id
FROM [friends]
INNER JOIN [user]
ON friends.this_friend_id = user.id
WHERE friends.this_friend_id = 3
union
SELECT user.id, friends.this_friend_id, friends.that_friend_id
FROM [friends]
INNER JOIN [user]
ON friends.that_friend_id = user.id
WHERE friends.that_friend_id = 3
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之后的where子句 join子句：
The WHERE clause goes after the JOIN clause(s):
因此，您已经有了错误的方式。简单查询的操作员顺序应为：
您的查询会变成：
但是使用或语句并不好，因为它会导致完整的表格扫描 如果您想创建一个更具性能的脚本，则可以在下面使用联合语句而不是or the the_friend_id and that_friend_id加入。
So you've got the order of operators the wrong way around. The operator order of a simple query should be:
So your query would turn into:
However using or statements is not great as it causes full scans of tables. If you wanted to create a more performant script you could do the below, where you use the union statement instead of the or to get this_friend_id and that_friend_id join.