Oracle数据库

        方式一（推荐）

-- 将 t2表的字段更新到t1表MERGE INTO COMMUnity_MEMBER_APPLY_DIE T1USING COMMUNITY_MEMBER T2ON (T1.MEMBER_ID = T2.MEMBER_ID)WHEN MATCHED THEN    UPDATE    SET T1.REAL_NAME = T2.USER_NAME,        T1.CARD_NUM=T2.CARDNUM    where T1.CARD_NUM is null       or T1.REAL_NAME is null;

        方式二

-- 将 t2表的字段更新到t1表update COMMUNITY_MEMBER_APPLY_DIE T1set (REAL_NAME, CARD_NUM)        = (select T2.USER_NAME, T2.CARDNUM from COMMUNITY_MEMBER T2 where T1.MEMBER_ID = T2.MEMBER_ID)where T1.CARD_NUM is null   or T1.REAL_NAME is null;

        方式一比方式二效率快很多

Mysql数据库 

-- 将 t2表的字段更新到t1表update org T1, community_area T2set T1.prov=T2.province,    T1.city=T2.city,    T1.dist=T2.district,    T1.street=T2.town,    T1.community=T2.villagewhere T1.area_code = T2.area_code;

来源地址：https://blog.csdn.net/codeMonkey_gxy/article/details/131601530