需要使用多個“ AND”轉換OUTER JOIN

Question

我有想要轉換為Esqueleto的原始sql。 它將所有未通過group_membership表注冊的用戶ID 1的group group_membership 。

SELECT * 
FROM group
LEFT OUTER JOIN group_membership
  ON (group.id = group_membership.group_id AND group_membership.user_id=1)
  WHERE group_membership.group_id IS NULL

Answer 1

這是我從不同問題中收集到的答案：

getGroups userId = do
    runDB
        . E.select
        . E.from $ \(group `E.LeftOuterJoin` groupMembership) -> do
            E.on $ E.just (group ^. GroupId) E.==. (groupMembership ?. GroupMembershipGroupId) &&.
                   (groupMembership ?. GroupMembershipUserId) E.==. E.just (E.val userId)
            E.where_ $ E.isNothing (groupMembership ?. GroupMembershipGroupId)
            return
              ( group ^. GroupId
              , group ^. GroupTitle
              )