sql 更新笔记

更新sql 

UPDATE test  t
SET brandcode = (
    SELECT
        `code`
    FROM
        ca_brand_code
    WHERE
        ca_brand_code.id = t.brandcode_Id
)
WHERE exists(select 1 from ca_brand_code t2 where t2.id = t.brandcode_Id);

删除记录

delete from 表名;
truncate table 表名;