目录

• 查看数据表中的记录
• 如何往数据表中添加数据记录
• 写法一
• 写法二
• 如何删除数据
• 如何修改数据

查看数据表中的记录

SELECt * from pet;

如果为空：

Empty set (0.03 sec)

如何往数据表中添加数据记录

写法一

 INSERT INTO pet VALUES ('Bob','John','hamster','f','2000-01-01',NULL);
 # Query OK, 1 row affected (0.02 sec) 

再次查询结果：

+------+-------+---------+------+------------+-------+
| name | owner | species | sex  | birth      | death |
+------+-------+---------+------+------------+-------+
| Bob  | John  | hamster | f    | 2000-01-01 | NULL  |
+------+-------+---------+------+------------+-------+
1 row in set (0.06 sec)

写法二

INSERT INTO pet(name,owner) VALUES ('Bob','John');

代表在name和owner字段上面插入的一条,其他皆为NULL/默认值的数据

(注意：NULL:代表的是空,表示该字段还没有数据.，一定要和’NULL’区分）

如何删除数据

先多添加几个数据

INSERT INTO pet VALUES('pp1','cc1','dog1','1','1998-1-2',null);
INSERT INTO pet VALUES('pp2','cc2','dog2','2','1998-2-2',null);
INSERT INTO pet VALUES('pp3','cc3','dog3','1','1998-3-2',null);
INSERT INTO pet VALUES('pp4','cc4','dog4','2','1998-4-2',null);

此时数据表中的记录：

+------+-------+---------+------+------------+-------+
| name | owner | species | sex  | birth      | death |
+------+-------+---------+------+------------+-------+
| Bob  | John  | hamster | f    | 2000-01-01 | NULL  |
| pp1  | cc1   | dog1    | 1    | 1998-01-02 | NULL  |
| pp2  | cc2   | dog2    | 2    | 1998-02-02 | NULL  |
| pp3  | cc3   | dog3    | 1    | 1998-03-02 | NULL  |
| pp4  | cc4   | dog4    | 2    | 1998-04-02 | NULL  |
+------+-------+---------+------+------------+-------+
5 rows in set (0.01 sec)

删除pp1这一行的数据：

 DELETe FROM pet where name='pp1';
 # name='pp1'换成owner='cc1'等等效果相同

此时数据表中的记录，pp1所在的第二行已被删除：

+------+-------+---------+------+------------+-------+
| name | owner | species | sex  | birth      | death |
+------+-------+---------+------+------------+-------+
| Bob  | John  | hamster | f    | 2000-01-01 | NULL  |
| pp2  | cc2   | dog2    | 2    | 1998-02-02 | NULL  |
| pp3  | cc3   | dog3    | 1    | 1998-03-02 | NULL  |
| pp4  | cc4   | dog4    | 2    | 1998-04-02 | NULL  |
+------+-------+---------+------+------------+-------+

如何修改数据

UPDATE tableName SET 字段1=值1,字段2=值2 ... WHERe 条件;

例如将pp2修改为pp22

 UPDATE pet SET name='pp22' WHERe owner='cc2';

此时数据表中的记录：

+------+-------+---------+------+------------+-------+
| name | owner | species | sex  | birth      | death |
+------+-------+---------+------+------------+-------+
| Bob  | John  | hamster | f    | 2000-01-01 | NULL  |
| pp22 | cc2   | dog2    | 2    | 1998-02-02 | NULL  |
| pp3  | cc3   | dog3    | 1    | 1998-03-02 | NULL  |
| pp4  | cc4   | dog4    | 2    | 1998-04-02 | NULL  |
+------+-------+---------+------+------------+-------+
4 rows in set (0.00 sec)