Oracle merge into 学习

用途

将A表的数据输出到B表中，根据条件判断B表中是否有数据，有则更新，没有则插入

语法

merge into table1 alias1    using table2 alias2    on (condition)when matched then    update set col1=col2when not matched then    insert (col1) values (col2)

示例

MERGE INTO SCOTT.TEST_USERS m0 USING (    SELECT        t0.USERID,        t0.USERNAME    FROM        SCOTT.USERS) m1 ON (m0.USERID = m1.USERID)WHEN MATCHED THEN    UPDATESET USERNAME = m1.USERNAMEWHEN NOT MATCHED THEN    INSERT (USERID, USERNAME)VALUES    (m1.USERID, m1.USERNAME)