sql学习笔记2-数据记录操作

1、mysql数据类型

可参考菜鸟教程，链接如下：
https://www.runoob.com/mysql/mysql-data-types.html
对于数据类型要按需使用，日期时间按格式，字符串数字按大小和长度

2、向表中插入数据

方式一：insert into 表名 values(各字段的值);
方式二：insert into 表名(字段1,字段2,...字段n）values（选中字段的值，其它为默认值或NULL)；

insert into pet values('狗','me','dog','1','2002-1-2');

或者

insert into pet('name','owner') values('猫','you');

3、查询插入的数据

select * from 表名；

select * from pet;

#返回结果
+------+-------+---------+------+------------+
| name | owner | species | sex  | brith      |
+------+-------+---------+------+------------+
| 狗   | me    | dog     | 1    | 2002-01-02 |
| you  | 猫    | NULL    | NULL | NULL       |
+------+-------+---------+------+------------+
2 rows in set (0.00 sec)

4、从表中删除数据

delete from 表名 where 条件；

delete from pet where name='狗';

#返回结果
Query OK, 1 row affected (0.03 sec)

mysql> select * from pet;
+------+-------+---------+------+-------+
| name | owner | species | sex  | brith |
+------+-------+---------+------+-------+
| you  | 猫    | NULL    | NULL | NULL  |
+------+-------+---------+------+-------+
1 row in set (0.01 sec)

5、修改表中数据

update 表名 set 字段1=值1,字段2=值2.... where 条件;

#原表
select *from pet;
+------+-------+---------+------+-------+
| name | owner | species | sex  | brith |
+------+-------+---------+------+-------+
| 猫   | 猫    | NULL    | NULL | NULL  |
+------+-------+---------+------+-------+
1 row in set (0.00 sec)

修改操作

update pet set owner='you' where specise is NULL;

#返回结果
mysql> select *from pet;
+------+-------+---------+------+-------+
| name | owner | species | sex  | brith |
+------+-------+---------+------+-------+
| 猫   | you   | NULL    | NULL | NULL  |
+------+-------+---------+------+-------+
1 row in set (0.01 sec)