我有一个city_id列,其中包含varchar(255)和null值。我想将其更改为大整数。
我会用:
ALTER TABLE Customer
ALTER COLUMN CITY_ID BIGINT
我是否松动或损坏了任何数据?
您可以尝试添加一个新的大整数列作为中间步骤:
-- add new column
ALTER TABLE Customer ADD COLUMN CITY_ID_NEW BIGINT;
-- populate new column
UPDATE Customer
SET CITY_ID_NEW = CAST(CITY_ID AS UNSIGNED);
-- drop old column and rename new column
ALTER TABLE Customer DROP COLUMN CITY_ID;
ALTER TABLE Customer CHANGE COLUMN CITY_ID_NEW CITY_ID BIGINT NULL DEFAULT NULL;
我假设您的整数值都是正数,即它们没有签名。如果需要有符号整数,则将更新中的强制转换更改为SIGNED
。