请教SQL查询语句问题。

MERGE INTO T1
USING T2
ON (T1.L1 = T2.L1)
WHEN MATCHED THEN
UPDATE
SET T1.L2=T2.L2
--有空可以看一下资料的内容,你会对MERGE的用法有更深刻的理解.
--看了一下问题补充,update语句的话,参照下面"相关子查询"写法
UPDATE T1
SET T1.L2=T2.L2
WHERE EXISTS (
SELECT 1
FROM T2
WHERE T1.L1 = T2.L1
)
--PS:推荐MERGE写法,更容易理解,效率更高,功能更强

是这样吗？
select distinct t1.l1, t2.l2 from t1, t2 where t1.l1 = t2.l1

select t1.l1, t2.l2 from t1 left join t2 on t1.l1 = t2.l1

update t1 set l2=(select distinct l2 from t2 where t1.l1=t2.l1)
where exists (select distinct l2 from t2 where t1.l1=t2.l1)

update T1(L2)
values(select L2 from T2)