MySQL修改某一列的前幾個字符

-- 用子查詢的值，替換掉前4個字符，驗證
SELECT
　　concat( ( SELECT city_code FROM business_department WHERE id = p.city ), RIGHT ( new_code, CHAR_LENGTH( new_code ) - 4 ) )
FROM
　　business_project p
ORDER BY
new_code DESC;

-- 更新
UPDATE business_project p
SET p.new_code = concat( ( SELECT city_code FROM business_department WHERE id = p.city ), RIGHT ( new_code, CHAR_LENGTH( new_code ) - 4 ) )

 

參考 https://www.zhihu.com/question/51964872