改变列的数据类型 [sql] ALTER TABLE visitor MODIFY nam VARCHAR(30); 追加新列 [sql] ALTER TABLE visitor ADD age INT; ALTER TABLE visitor ADD age INT FIRST; ALTER TABLE visitor ADD age INT AFTER nam; 改变列的位置 [sql] ALTER TABLE visitor MODIFY age INT AFTER nam; 改变列名 和 类型 [sql] ALTER TABLE visitor CHANGE birth birthday DATE; 删除列 [sql] ALTER TABLE visitor DROP age; 表的复制 [sql] CREATE TABLE customerH SELECT * FROM customer; CREATE TABLE customerG LIKE customer; INSERT INTO customerG SELECT * FROM customer; INSERT INTO tb1G(no) SELECT bang FROM tb1; 表的删除 [sql] DROP TABLE IF EXISTS customerG; DROP TABLE customerG;