Question

请查看以下查询：

SELECT distinct a.*, coalesce (r.email,r2.email) as 'sign_in_email'
into #adobe_prep
FROM dbo.adobe 
left join 
dbo.registration r ON (a.user_id = r.up_user_id)
left join 
dbo.registration r2 ON (a.user_id = r2.entity_id)

我基本上尝试将a.user_id与r.up_user_id匹配，如果与up_user_id不匹配，则匹配entity_id。但是，这个语句没有条件，所以我得到重复，因为有时a.user_id = r.up_user_id但是a.user_id = r2.entity_id（仅用于不同的值）。你能帮忙添加条件，只有当a.user_id＆lt;＆gt;时才会出现第二个左连接。 r.up_user_id？

Answer 1

但你自己写了答案！尝试添加您用文字写的条件：

and a.user_id <> r.up_user_id

像这样：

select distinct a.*, coalesce (r.email,r2.email) as 'sign_in_email'
into #adobe_prep
from dbo.adobe 
          left join dbo.registration r ON (a.user_id = r.up_user_id)
          left join dbo.registration r2 ON (a.user_id = r2.entity_id and a.user_id <> r.up_user_id)

添加条件到第二个左连接

1 个答案: