查询以在比表 A 中的记录更新时从表 B 返回值

Question

我有一个表格，其中包含成员的姓名、地址等，以及上次更新记录的时间戳。我有第二个表，它保存对成员记录的更新，一个保存表，直到更改得到工作人员的批准。

我有一个从成员表返回数据的查询。我现在需要检查更新表，如果更新表中的成员记录具有更新的时间戳，则返回该记录而不是成员表中的记录。

我尝试了一些方法，例如 UNION 和 Top 1，但不太正确。我可以做一个复杂的CASE 声明，但这样会表现良好吗？

听起来很简单，从表 A 中获取最新的记录，从表 B 中获取最新的记录，然后返回最新的一条记录。

SELECT name, address, city, state, zipcode, time_stamp
FROM Member
WHERE ID = 123

SELECT name, address, city, state, zipcode, time_stamp
FROM MemberUpdates
WHERE ID = 123

编辑：

好的，在目前的帮助下，我能够得到预期的结果。然后，我去添加额外的 where 子句，我打破了它。尝试了几种不同的方法，包括使用 CTE，但无法完全正确。这是一个有效并返回预期结果的查询，但请注意我必须传递 name_last/birth_year/memNum 两次。有没有更好的办法？

SELECT TOP 1 m.abn,
            m.aliases,
            m.birth_year,
            m.user_stamp, 

            q.updatePending,
            q.name_first,
            q.name_last,
            q.company,
            q.address1,
            q.mailing_address,
            q.city,
            q.state,
            q.zipcode,
            q.email_address

FROM (
                        SELECT  TOP 1   
                            1 AS updatePending, 
                            a.entity_number,
                            a.name_first,
                            a.name_last,
                            NULLIF(LTRIM(RTRIM(
                            LTRIM(RTRIM(ISNULL(a.company, ''))) +
                            LTRIM(RTRIM(ISNULL(a.firm_name, ''))))),'') AS company,
                            a.address1,
                            a.mailing_address,
                            a.city,
                            a.state,
                            a.zip_code AS zipcode,
                            a.internet_address AS email_address,
                            a.time_stamp
            FROM        statebar.dbo.STAGING_Address_Change_Request a
                INNER JOIN Member m ON m.entity_number = a.entity_number
            WHERE       a.entity_number = (
    SELECT m.entity_number
    FROM Member m
        INNER JOIN  Named_Entity ne ON  (ne.entity_number = m.entity_number)
    WHERE   ne.name_last = 'jones'
        AND m.birth_year = '1975'
        AND m.memNum = '12345'
        )
                AND a.time_stamp > m.time_stamp

            UNION ALL

            SELECT TOP 1 
                    0 AS updatePending,
                    ne.entity_number,
                    ne.name_first,
                    ne.name_last,
                    NULLIF(LTRIM(RTRIM(
                    LTRIM(RTRIM(ISNULL(ne.company, ''))) +
                    LTRIM(RTRIM(ISNULL(ne.firm_name, ''))))),'') AS company,
                    ne.address1,
                    ne.mailing_address,
                    ne.city,
                    ne.state,
                    ne.zip_code,
                    ne.internet_address AS email_address,
                    m.time_stamp
            FROM    Member m
                INNER JOIN  Named_Entity ne ON  (ne.entity_number = m.entity_number)
                LEFT JOIN   statebar.dbo.STAGING_Address_Change_Request a ON a.entity_number = m.entity_number
            WHERE   ne.entity_number = (
                                        SELECT m.entity_number
                                        FROM Member m
                                            INNER JOIN  Named_Entity ne ON  (ne.entity_number = m.entity_number)
                                        WHERE   ne.name_last = 'jones'
                                            AND m.birth_year = '1975'
                                            AND m.memNum = '12345'
                                            )
                AND m.time_stamp > a.time_stamp
            ORDER BY updatePending DESC, a.time_stamp DESC) q
    INNER JOIN Member m on m.entity_number = q.entity_number

ORDER BY q.time_stamp DESC 

Answer 1

这是一个简单的查询，可以帮助您返回最近的记录：

--Only selects the top row with the most recent record
SELECT TOP 1 * FROM record
(
    --Select rows with the same ID
    SELECT name, address, city, state, zipcode, time_stamp
    FROM Member
    WHERE ID = 123
    UNION ALL
    SELECT name, address, city, state, zipcode, time_stamp
    FROM MemberUpdates
    WHERE ID = 123
) t
ORDER BY t.time_stamp DESC --Order the table by time_stamp to get the most recent record
-- DESC is used because datetime is ordered by oldest first in ascending order.

Answer 2

联合方法是个好主意，但您可能希望使用row_number() 窗口函数，而不仅仅是顶部。此外，可以使用union all 代替union。你不必关心A 和B 之间的重复，union all 只会表现得更好：

SELECT name, address, city, state, zipcode, time_stamp
FROM   (SELECT name, address, city, state, zipcode, time_stamp, 
               ROW_NUMBER() OVER (PARTITION BY name ORDER BY time_stamp DESC) rn
        FROM   (SELECT name, address, city, state, zipcode, time_stamp
                FROM   Member
                UNION ALL
                SELECT name, address, city, state, zipcode, time_stamp
                FROM   MemberUpdates) t
        ) q
WHERE   rn = 1

Answer 3

考虑：

SELECT
    id,
    MAX(CASE WHEN u.mx_ts IS NULL THEN m.mx_ts ELSE u.mx_ts end)
FROM 
    (SELECT 
        id, 
        MAX(time_stamp) AS mx_ts 
    FROM 
        MEMBER 
    GROUP BY 
        id) m
    LEFT OUTER JOIN
    (SELECT 
        id, 
        MAX(time_stamp) AS mx_ts 
    FROM 
        MemberUpdates 
    GROUP BY 
        id) u ON
    m.id = u.id AND
    u.mx_ts > m.mx_ts
GROUP BY 
    id

这将加入来自memberupdates 的每个 id 的后续时间戳（如果有的话）。否则，您可以使用 member 表中每个 id 的最新时间戳。