mysql怎么修改字段

ALTER TABLE table_name RENAME COLUMN old_column_name TO new_column_name;

ALTER TABLE table_name MODIFY column_name new_data_type;

ALTER TABLE table_name ALTER COLUMN column_name SET DEFAULT new_default_value;

ALTER TABLE table_name MODIFY column_name data_type FIRST; -- 将字段移动到表的最前面
ALTER TABLE table_name MODIFY column_name data_type AFTER another_column; -- 将字段移动到另一个字段之后

ALTER TABLE users MODIFY age SMALLINT;

UPDATE users SET age = 0 WHERE age > 32767; -- 假设新的数据类型是 SMALLINT，范围是 -32768 到 32767
ALTER TABLE users MODIFY age SMALLINT;

CREATE TABLE users_backup AS SELECT * FROM users; -- 备份数据
DELETE FROM users; -- 清空表中的数据
ALTER TABLE users MODIFY age SMALLINT; -- 修改字段的数据类型
INSERT INTO users SELECT * FROM users_backup; -- 将数据重新导入表中