merge实现拉链表

建表如下（ 历史拉链表）：

新表（每日更新的）：

 

 

实现语句：

MERGE INTO test_target t1
USING (
    SELECT nvl(c.id, b.id) AS id
        ,CASE 
            WHEN c.endtime = to_date('9999-12-30', 'yyyy-mm-dd')
                AND b.id IS NULL
                THEN c.STATUS
            WHEN c.id IS NULL
                THEN b.STATUS
            END AS STATUS
        ,CASE 
            WHEN c.endtime = to_date('9999-12-30', 'yyyy-mm-dd')
                AND b.id IS NULL
                THEN c.begain
            WHEN c.id IS NULL
                THEN to_date('2017-03-15', 'yyyy-mm-dd')
            END AS begain
        ,CASE 
            WHEN c.endtime = to_date('9999-12-30', 'yyyy-mm-dd')
                AND b.id IS NULL
                THEN to_date('2017-03-15', 'yyyy-mm-dd')
            WHEN c.id IS NULL
                THEN to_date('9999-12-30', 'yyyy-mm-dd')
            END AS endtime
    FROM test_b b
    FULL JOIN test_target c ON b.id = c.id
        AND b.STATUS = c.STATUS
    WHERE c.id IS NULL
        OR (
            c.endtime = to_date('9999-12-30', 'yyyy-mm-dd')
            AND b.id IS NULL
            )
    ) t2
    ON (
            t1.id = t2.id
            AND t1.STATUS = t2.STATUS
            )
WHEN MATCHED
    THEN
        UPDATE
        SET t1.endtime = t2.endtime
        WHERE t1.endtime = to_date('9999-12-30', 'yyyy-mm-dd')
WHEN NOT MATCHED
    THEN
        INSERT
        VALUES (
            t2.id
            ,t2.STATUS
            ,t2.begain
            ,t2.endtime
            );

 

 结果如下：