超过1个OR的mysql SELECT

Question

I am trying to make a numrows query to see if the user is friends with the other user, by doing user1 and user2.

Here is my query, but this doesn't work.

SELECT * FROM friends 
WHERE friend1 = USER_ID
AND friend2 = FRIEND
OR
WHERE friend1 = FRIEND
AND friend2 = USER_ID

So the query is checking to see it in both ways, back to front, how do I make this possible.

Answer 1

You can only have one WHERE in a SQL statement, so you would want to use something like:

SELECT * 
FROM friends 
WHERE 
(
  friend1 = USER_ID
  AND friend2 = FRIEND
) 
OR
(
  friend1 = FRIEND
  AND friend2 = USER_ID
) 

The parentheses are not required due to operator precedence, I used them for clarity.

Answer 2

您是否尝试使用括号？

SELECT * FROM friends WHERE (friend1 = USER_ID AND friend2 = FRIEND) OR (WHERE friend1 = FRIEND AND friend2 = USER_ID)