MYSQL - 插入、更新、删除

执行这些操作的3个关键字：

• INSERT
• UPDATE
• DELETE

MYSQL插入数据 - INSERT INTO table_name

INSERT可以做的事情：

• 为所有字段插入数据
• 为部分字段插入数据

INSERT INTO table_name (column_list) VALUES (value_list);

• 插入多行数据

INSERT INTO table_name (column_list)
VALUES (value_list1), (value_list2), ...,(value_listn);

• 将查询结果插入表中

INSERT INTO table_name (column_list1)
SELECT (column_list2) FROM table_name2 WHERE (condition);

MYSQL更新数据 - UPDATE table_name SET

UPDATE table_name
SET column_name1 = value1, column_name2 = value2, ... ,column_namen = valuen
WHERE (condition);

MYSQL删除数据 - DELETE FROM table_name

DELETE FROM table_name [WHERE <contition>];

删除表 - TRUNCATE TABLE

TRUNCATE TABLE直接删除表，再创建一个新表；所以速度比DELETE快。

TRUNCATE TABLE table_name;

为表增加计算列

操作的语法如下：

col_name data_type [GENERATED ALWAYS] AS (expression)
[VIRTUAL | STORED] [UINQUE [KEY]] [COMMENT comment]
[NOT NULL | NULL] [[PRIMARY] KEY]

示例：

CREATE TABLE tb1(
id int(9) NOT NULL AUTO_INCREMENT,
a int(9) DEFAULT NULL,
b int(9) DEFAULT NULL,
c int(9) GENERATED ALWAYS AS ((a+b)) VIRTUAL,
PRIMARY KEY (`id`)
);