1 使用select语句查询一个数据表 select* from 数据表名; 2 查询表中的一个字段或多个字段 select 字段1,字段2 from 数据表; 3 查询表中指定的数据信息 select* from数据表名order by id desc limit 2,1; //查询的数据按id倒序排序 4 查询指定路径 Select* f
select* from 数据表名;
select 字段1,字段2 from 数据表;
select* from数据表名order by id desc limit 2,1; //查询的数据按id倒序排序
Select* from 数据表 where 属性 = ‘…’;
Select* from 数据表 where 字段 [NOT] IN (字段值1，字段值2…字段值n);
<注：最适于数组作为查询条件，即：in (数组数据)>
例如：
mysql>select * from library where price in (99,50);
+----+--------------+--------+-------+
| id | name | author |price |
+----+--------------+--------+-------+
| 1 | java范例大全 | 张帆 | 99 |
| 2 | mySQL | 潘凯华 | 50 |
+----+--------------+--------+-------+
mysql>select * from library where price NOT IN(99,50);
+----+---------------+--------+-------+
| id | name | author| price |
+----+---------------+--------+-------+
| 3 | SQLserver2005 | 刘智勇 | 80 |
+----+---------------+--------+-------+
select * from 数据表 where 字段 [NOT] BETWEEN 取值1 and 取值2；
例如：
mysql> select * from country where idBETWEEN 2 and 4;
+----+----------+------------+------+----------+
| id | name | population | area | language |
+----+----------+------------+------+----------+
| 2 | American | 4 | 60 | English |
| 3 | Japan | | 30 | Jpanese |
| 4 | England | 2 | 300 | English |
+----+----------+------------+------+----------+
3 rows in set(0.09 sec)
mysql> select* from country where id NOT BETWEEN 2 and 4;
+----+-------+------------+------+----------+
| id | name | population | area | language |
+----+-------+------------+------+----------+
| 1 | china | 13 | 960 | chinese |
+----+-------+------------+------+----------+
(1) select * from 数据表 where 属性 like '%SQL%'；//查询属性中包含SQL字符的数据
(2) select * from 数据表 where 属性 like 'a%b';// //查询属性中以a开头以b结尾的字符串的数据
(3) select * from 数据表 where 属性 like 'm_n';//查询属性中以m开头以n结尾的3个字符的数据，中间的‘_’只能代表一个字符
例如：
mysql> select * from library where name like '%SQL%';
+----+---------------+--------+-------+
| id | name | author| price |
+----+---------------+--------+-------+
| 2 | mySQL | 潘凯华 | 50 |
| 3 | SQLserver2005 | 刘智勇 | 80 |
+----+---------------+--------+-------+
mysql> select * from library where name like 'myS_L';
+----+-------+--------+-------+
| id | name | author | price|
+----+-------+--------+-------+
| 2 | mySQL | 潘凯华 | 50 |
+----+-------+--------+-------+
mysql> select * from library whereprice=50 and name like 'myS_L';
+----+-------+--------+-------+
| id | name | author | price |
+----+-------+--------+-------+
| 2 | mySQL | 潘凯华 | 50 |
+----+-------+--------+-------+
mysql> select * from library where price=50or price=99;
+----+--------------+--------+-------+
| id | name | author | price |
+----+--------------+--------+-------+
| 1 | java范例大全 | 张帆 | 99 |
| 2 | mySQL | 潘凯华 | 50 |
+----+--------------+--------+-------例如：
原表：mysql> select * from library;
+----+---------------+--------+-------+
| id | name | author | price |
+----+---------------+--------+-------+
| 1 | java范例大全 | 张帆 | 99 |
| 2 | mySQL | 潘凯华 | 50 |
| 3 | SQLserver2005 | 刘智勇 | 80 |
| 4 | mySQL | 李慧 | 50 |
+----+---------------+--------+-------+
mysql> select distinct name fromlibrary;
+---------------+
| name |
+---------------+
| java范例大全 |
| mySQL |
| SQLserver2005 |
+---------------+
mysql> select * from library orderby id desc;//倒序排列
+----+---------------+--------+-------+
| id | name | author | price |
+----+---------------+--------+-------+
| 4 | mySQL | 李慧 | 50 |
| 3 | SQLserver2005 | 刘智勇 | 80 |
| 2 | mySQL | 潘凯华 | 50 |
| 1 | java范例大全 | 张帆 | 99 |
+----+---------------+--------+-------+
mysql> select * from library orderby id asc;//正序排列
+----+---------------+--------+-------+
| id | name | author | price |
+----+---------------+--------+-------+
| 1 | java范例大全 | 张帆 | 99 |
| 2 | mySQL | 潘凯华 | 50 |
| 3 | SQLserver2005 | 刘智勇 | 80 |
| 4 | mySQL | 李慧 | 50 |
+----+---------------+--------+-------+
(1) 用GROUP BY关键字分组查询
例如：mysql> select name,price from library GROUP BY price;
+---------------+-------+
| name | price |
+---------------+-------+
| mySQL | 50 |
| SQLserver2005 | 80 |
| java范例大全 | 99 |
+---------------+-------+
3 rows in set (0.00 sec)
mysql> select name,price from library GROUP BY name;
+---------------+-------+
| name | price |
+---------------+-------+
| java范例大全 | 99 |
| mySQL | 50 |
| SQLserver2005 | 80 |
+---------------+-------+
(2) GROUP BY 关键字与 GROU_CONCAT函数一起使用
mysql> selectname,GROUP_CONCAT(price) from library GROUP BY name;
+---------------+---------------------+
| name |GROUP_CONCAT(price) |
+---------------+---------------------+
| java范例大全 | 99 |
| mySQL | 50,50 |
| SQLserver2005 | 80 |
+---------------+---------------------+
（3）按多个字段进行分组
mysql> selectid,name,price from library GROUP BY name,price;//当price字段的值相等时，再按照name字段分组
+----+---------------+-------+
| id |name | price |
+----+---------------+-------+
| 1 | java范例大全 | 99 |
| 2 | mySQL | 50 |
| 3 | SQLserver2005 | 80 |
+----+---------------+-------+
mysql> select * from library orderby id asc limit 2,3; //取两条数据，正序，从第三条开始
+----+---------------+--------+-------+
| id | name | author | price |
+----+---------------+--------+-------+
| 3 | SQLserver2005 | 刘智勇 | 80 |
| 4 | mySQL | 李慧 | 50 |
+----+---------------+--------+-------+
2 rows in set (0.00 sec)
mysql> select * from libraryorder by id desc limit 2,3; //取两条数据，倒序，从倒数第三条结束，只显示倒数前两个
+----+--------------+--------+-------+
| id | name | author | price |
+----+--------------+--------+-------+
| 2 | mySQL | 潘凯华 | 50 |
| 1 | java范例大全 | 张帆 | 99 |
+----+--------------+--------+-------+
