DDL

INSERT

• 插入单条记录

INSERT INTO user (username, password, age) VALUES ('zhangsan', '123456', 20);

• 插入多条记录

INSERT INTO user (name, age) VALUES 
('张三', 20),
('李四', 25);

UPDATE

• 修改单个字段

UPDATE user SET age = 25 WHERE id = 1;

• 修改多个字段

UPDATE user  SET name = '王五',age = 30,status = 0 WHERE id = 1;

• 使用表达式修改

UPDATE 表名
SET stock = stock - 1
WHERE id = 1;

DELETE

DELETE FROM user WHERE id = 1;