MERGE INTO a 
USING b
ON ( a.id = b.id )    -- 条件是 id 相同
WHEN MATCHED THEN UPDATE SET a.name  = b.name    -- 匹配的时候，更新
WHEN NOT MATCHED THEN INSERT(a.id,a.name) VALUES(b.id, b.name) -- 源表有，目标表没有，插入