将来自查询的非重复值插入另一个表

Question

我有以下查询，该查询使我返回cookie_hash，crdate，account_uuid和action列。

SELECT DISTINCT ON (cookie_hash) event.cookie_hash, event.crdate, event.account_uuid, event.action
FROM event
WHERE cookie_hash IN (SELECT community_signup.cookie_hash FROM community_signup) AND 
event.action = 'signup'
ORDER BY cookie_hash, crdate DESC;

然后我有另一个表community_signup，其中填充了列cookie_hash，空列为crdate和account_uuid。

我如何用cookie_hash的相应值填充table2中的空列？

Answer 1

我希望这对您有用。

 UPDATE A
    SET A.crdate =B.crdate,
    A.account_uuid = B.account_uuid
    FROM community_signup AS A
    INNER JOIN 
    (
    SELECT Distinct cookie_hash, crdate, account_uuid, [action]
    FROM [event] WHERE cookie_hash IN (SELECT community_signup.cookie_hash FROM community_signup) AND 
    event.action = 'signup'
    ORDER BY cookie_hash, crdate DESC
    )AS B
    ON A.cookie_hash = B.cookie_hash

Answer 2

在UPDATE使用FROM子句。 Postgres语法如下所示：

UPDATE community_signup cs
    SET crdate = e.crdate,
        account_uuid = e.account_uuid
FROM (SELECT DISTINCT ON (e.cookie_hash) e.cookie_hash, e.crdate, e.account_uuid, e.action
      FROM event e
      WHERE e.cookie_hash IN (SELECT cs.cookie_hash
                              FROM community_signup cs
                             ) AND 
            e.action = 'signup'
      ORDER BY e.cookie_hash, e.crdate DESC         
     ) 
WHERE e.cookie_hash = cs.cookie_hash;

请注意，我添加了表别名，因此查询更易于编写和阅读。

同样， IN过滤器并不是真正必需的。 外部WHERE也将处理该问题。