SQL复习——04

SQL INSERT INTO 语句

INSERT INTO 语句用于向表中插入新记录

INSERT INTO 语法

INSERT INTO table_name
VALUES (value1,value2,value3,...);
INSERT INTO table_name(column1,column2,column3,...)
VALUES(value1,value2,value3,...);

INSERT INTO 实例

INSERT INTO Websites(name,url,alexa,country)
VALUES('百度'，'https://www.baidu.com/','4','CN');

SQL UPDATE 语句

UPDATE语句用于更新表中已经存在的记录

SQL UPDATE 语法

UPDATE table_name
SET column1=value1,column2=value2,...
WHERE some_column=some_value;

SQL UPDATE 实例

UPDATE Websites
SET alexa='5000',country='USA'
WHERE name='一二三'

SQL DELETE 语句

DELETE 语句用于删除表中的记录

SQL DELETE 语法

DELETE FROM table_name
WHERE some_column=some_value;

SQL DELETE 实例

DELETE FROM Websites
WHERE name='百度' AND country='CN'

删除所有数据

可以在不删除表的情况下，删除表中的所有行。这意味着表结构、索引、属性将保持不变：

DELETE FROM table_name;
DELETE * FROM table_name;