Mysql查询语法（读mysql必知必会有感）
通过看Mysql必知必会，发现里面讲的表的查询挺详细的，以下是我的看后的总结。
里面全是Mysql 的查询语句。从最基础的到难的。
先看看数据库的结构。
MariaDB [CargoWarehouse]> show tables;
+--------------------------+
| Tables_in_CargoWarehouse |
+--------------------------+
| customers |
| orderitems |
| orders |
| productnotes |
| products |
| vendors |
+--------------------------+
6 rows in set (0.00 sec)
分别是：
customers表，存储着所有客户的信息
orderitems表，每个订单的实际物品
orders表，存储着顾客的订单
productnotes表，存储与特定产品相关的注释
products表，包含着产品目录
venders表，存储着销售产品的供应商
一.最简单的select检索
1.查products中的产品名字
MariaDB [CargoWarehouse]> select prod_name from products;
+----------------+
| prod_name |
+----------------+
| .5 ton anvil |
| 1 ton anvil |
| 2 ton anvil |
| Detonator |
| Bird seed |
| Carrots |
| Fuses |
| JetPack 1000 |
| JetPack 2000 |
| Oil can |
| Safe |
| Sling |
| TNT (1 stick) |
| TNT (5 sticks) |
+----------------+
14 rows in set (0.00 sec)2.查看都有哪些值（相同重复的只显示一遍）
如果不用distinct的话，会显示所有的id值。包括重复的。（本来一共14行呢）
MariaDB [CargoWarehouse]> select distinct vend_id from products;
+---------+
| vend_id |
+---------+
| 1001 |
| 1002 |
| 1003 |
| 1005 |
+---------+
4 rows in set (0.00 sec)
3.限制结果
这个是显示输出从第4行开始的6行（也就是4,5,6,7,8,9行）
MariaDB [CargoWarehouse]> select vend_id from products limit 3,6;
+---------+
| vend_id |
+---------+
| 1002 |
| 1002 |
| 1003 |
| 1003 |
| 1003 |
| 1003 |
+---------+
6 rows in set (0.00 sec)
二.排序检索数据
1.倒序输出
因为默认就是升序（ASC）的，所以我只介绍降序（DESC）的（以价格的降序来输出）
order by 是以谁的顺序去排整张表
MariaDB [CargoWarehouse]> select prod_id,prod_price,prod_name from products order by prod_price desc limit 6;
+---------+------------+----------------+
| prod_id | prod_price | prod_name |
+---------+------------+----------------+
| JP2000 | 55.00 | JetPack 2000 |
| SAFE | 50.00 | Safe |
| JP1000 | 35.00 | JetPack 1000 |
| ANV03 | 14.99 | 2 ton anvil |
| DTNTR | 13.00 | Detonator |
| TNT2 | 10.00 | TNT (5 sticks) |
+---------+------------+----------------+
6 rows in set (0.00 sec)
2.和distinct 限制一起使用
MariaDB [CargoWarehouse]> select distinct vend_id from products order by prod_price desc;
+---------+
| vend_id |
+---------+
| 1005 |
| 1003 |
| 1001 |
| 1002 |
+---------+
4 rows in set (0.00 sec)
三.数据过滤
1.where过滤（注意order by的位置）
MariaDB [CargoWarehouse]> select prod_name,prod_price from products where prod_price >= 10 order by prod_price desc;
+----------------+------------+
| prod_name | prod_price |
+----------------+------------+
| JetPack 2000 | 55.00 |
| Safe | 50.00 |
| JetPack 1000 | 35.00 |
| 2 ton anvil | 14.99 |
| Detonator | 13.00 |
| Bird seed | 10.00 |
| TNT (5 sticks) | 10.00 |
+----------------+------------+
7 rows in set (0.00 sec)
2.不匹配检查
用 <> 不匹配检查，也可以使用!= （建议用这个）
MariaDB [CargoWarehouse]> select vend_id,prod_name from products where vend_id <> 13 limit 5;
+---------+--------------+
| vend_id | prod_name |
+---------+--------------+
| 1001 | .5 ton anvil |
| 1001 | 1 ton anvil |
| 1001 | 2 ton anvil |
| 1003 | Detonator |
| 1003 | Bird seed |
+---------+--------------+
5 rows in set (0.00 sec)
3.在哪个范围之内
MariaDB [CargoWarehouse]> select vend_id,prod_name,prod_price from products where prod_price between 5 and 10;
+---------+----------------+------------+
| vend_id | prod_name | prod_price |
+---------+----------------+------------+
| 1001 | .5 ton anvil | 5.99 |
| 1001 | 1 ton anvil | 9.99 |
| 1003 | Bird seed | 10.00 |
| 1002 | Oil can | 8.99 |
| 1003 | TNT (5 sticks) | 10.00 |
+---------+----------------+------------+
5 rows in set (0.00 sec)
这里的与或逻辑操作。and ，or
当然还可以使用IN（推荐使用）
MariaDB [CargoWarehouse]> select vend_id,prod_name,prod_price from products where prod_price in (5,10);
+---------+----------------+------------+
| vend_id | prod_name | prod_price |
+---------+----------------+------------+
| 1003 | Bird seed | 10.00 |
| 1003 | TNT (5 sticks) | 10.00 |
+---------+----------------+------------+
2 rows in set (0.00 sec)
4.检查空值
MariaDB [CargoWarehouse]> select cust_id from customers where cust_email is null;
+---------+
| cust_id |
+---------+
| 10002 |
| 10005 |
+---------+
2 rows in set (0.00 sec)
5.通配符进行过滤（LIKE）
这里 % 就好像是linux通配符里的* 。表示任何字符出现任意次数
这里就是jet开头的就行了
MariaDB [CargoWarehouse]> select prod_id,prod_name from products where prod_name like 'jet%';
+---------+--------------+
| prod_id | prod_name |
+---------+--------------+
| JP1000 | JetPack 1000 |
| JP2000 | JetPack 2000 |
+---------+--------------+
2 rows in set (0.00 sec)
这里是以s开头e结尾
MariaDB [CargoWarehouse]> select prod_name from products where prod_name like 's%e';
+-----------+
| prod_name |
+-----------+
| Safe |
+-----------+
1 row in set (0.00 sec)
这里的‘_’就相当于linux的通配符‘?’表示只匹配单个字符
MariaDB [CargoWarehouse]> select prod_id,prod_name from products where prod_name like '_ ton anvil';
+---------+-------------+
| prod_id | prod_name |
+---------+-------------+
| ANV02 | 1 ton anvil |
| ANV03 | 2 ton anvil |
+---------+-------------+
2 rows in set (0.00 sec)
6.正则表达式进行过滤
正则匹配是用regexp进行匹配,也可以使用rlike
用过sed正则都知道，正则是很强大的。
‘.’一个点表示的是单一一个字符。和通配的_一样。
MariaDB [CargoWarehouse]> select prod_name from products
-> where prod_name regexp '.000' order by prod_name;
+--------------+
| prod_name |
+--------------+
| JetPack 1000 |
| JetPack 2000 |
+--------------+
2 rows in set (0.00 sec)
其中任意一个都可以
| 表示或的意思
MariaDB [CargoWarehouse]> select prod_name
-> from products
-> where prod_name regexp '1000|2000'
-> order by prod_name;
+--------------+
| prod_name |
+--------------+
| JetPack 1000 |
| JetPack 2000 |
+--------------+
2 rows in set (0.00 sec)
MariaDB [CargoWarehouse]> select prod_name from products
-> where prod_name regexp '[123]';
+---------------+
| prod_name |
+---------------+
| 1 ton anvil |
| 2 ton anvil |
| JetPack 1000 |
| JetPack 2000 |
| TNT (1 stick) |
+---------------+
5 rows in set (0.00 sec)
其中声明一下。以下字符代表的是前面的重复的
* 前面的字符重复0次或者无数次
+ 前面的字符重复1次或者无数次
{n} 前面的字符重复n次
{n,}前面的字符重复至少n次
{n,m}前面的字符重复n到m次
MariaDB [CargoWarehouse]> select prod_name
-> from products
-> where prod_name regexp '[[:digit:]]{2,}'
-> order by prod_name;
+--------------+
| prod_name |
+--------------+
| JetPack 1000 |
| JetPack 2000 |
+--------------+
2 rows in set (0.00 sec)
定位元字符
^ 文本的开始
$ 文本的结尾
[[:<:]] 词的开始
[[:>:]] 词的结尾
MariaDB [CargoWarehouse]> select prod_name
-> from products
-> where prod_name regexp 'vil[[:>:]]'
-> order by prod_name;
+--------------+
| prod_name |
+--------------+
| .5 ton anvil |
| 1 ton anvil |
| 2 ton anvil |
+--------------+
3 rows in set (0.00 sec)
四.创建计算字段
1.拼接一个字段
这里使用了concat函数，将两个字段合并成了一个字段输出。比如将产品名字后直接跟价格输出
还可以使用as给新组成的字段起一个新的名字。
MariaDB [CargoWarehouse]> select concat(prod_name,' (',prod_price,')')
-> as products
-> from products
-> order by prod_price desc;
+--------------------------+
| products |
+--------------------------+
| JetPack 2000 (55.00) |
| Safe (50.00) |
| JetPack 1000 (35.00) |
| 2 ton anvil (14.99) |
| Detonator (13.00) |
| TNT (5 sticks) (10.00) |
| Bird seed (10.00) |
| 1 ton anvil (9.99) |
| Oil can (8.99) |
| .5 ton anvil (5.99) |
| Sling (4.49) |
| Fuses (3.42) |
| Carrots (2.50) |
| TNT (1 stick) (2.50) |
+--------------------------+
14 rows in set (0.00 sec)
2.执行算数计算
直接使用*将两个数字字段乘起来。最好再使用一个as给该新的字段起一个名字
MariaDB [CargoWarehouse]> select prod_id,quantity,item_price,quantity*item_price as expanded_price
-> from orderitems
-> where order_num = 20005;
+---------+----------+------------+----------------+
| prod_id | quantity | item_price | expanded_price |
+---------+----------+------------+----------------+
| ANV01 | 10 | 5.99 | 59.90 |
| ANV02 | 3 | 9.99 | 29.97 |
| TNT2 | 5 | 10.00 | 50.00 |
| FB | 1 | 10.00 | 10.00 |
+---------+----------+------------+----------------+
4 rows in set (0.00 sec)
3.使用函数
使用now（）函数返回当前的操作时间。
MariaDB [CargoWarehouse]> select now() as operate_time,prod_id,item_price
-> from orderitems;
+---------------------+---------+------------+
| operate_time | prod_id | item_price |
+---------------------+---------+------------+
| 2017-01-11 14:14:55 | ANV01 | 5.99 |
| 2017-01-11 14:14:55 | ANV02 | 9.99 |
| 2017-01-11 14:14:55 | TNT2 | 10.00 |
| 2017-01-11 14:14:55 | FB | 10.00 |
| 2017-01-11 14:14:55 | JP2000 | 55.00 |
| 2017-01-11 14:14:55 | TNT2 | 10.00 |
| 2017-01-11 14:14:55 | FC | 2.50 |
| 2017-01-11 14:14:55 | FB | 10.00 |
| 2017-01-11 14:14:55 | OL1 | 8.99 |
| 2017-01-11 14:14:55 | SLING | 4.49 |
| 2017-01-11 14:14:55 | ANV03 | 14.99 |
+---------------------+---------+------------+
11 rows in set (0.00 sec)
五.使用数据处理函数
1.文本处理函数
下面只介绍几个简单的函数
upper（）将字符串转换为大写的
lower（）将字符串转为小写的
substring（）找出串中的字符内容
sounddex（）返回发音相似的串
我觉得其他的都还好理解。就最后一个需要说一下。soundex（）返回的发音相似的串。
比如我现在想找一个姓李的顾客。但不知道到底是Lee还是Lie。这时候就可以使用soundex（）了
MariaDB [CargoWarehouse]> select cust_name,cust_contact
-> from customers
-> where soundex(cust_contact) = soundex('Y Lie');
+-------------+--------------+
| cust_name | cust_contact |
+-------------+--------------+
| Coyote Inc. | Y Lee |
+-------------+--------------+
1 row in set (0.00 sec)
2.时间处理函数
adddate（） 增加一个日期
addtime（） 增加一个时间
curtime（） 当前时间
curdate（） 当前日期
date（） 返回一个日期的日期部分
dateoff（） 计算两个时间之差
year（） 返回一个时间的年的部分
month（） 返回一个时间的月的部分
day（） 返回一个时间的天的部分
hour（） 返回一个时间的小时部分
minute（） 返回一个时间的分钟的部分
Database changed
MariaDB [CargoWarehouse]> select cust_id,order_date
-> from orders
-> where date(order_date) = '2005-09-01';
+---------+---------------------+
| cust_id | order_date |
+---------+---------------------+
| 10001 | 2005-09-01 00:00:00 |
+---------+---------------------+
1 row in set (0.00 sec)
3.数学处理函数
abs（）绝对值
pi（）π值
rand（）返回一个随机数
sqrt（）返回平方根
4.聚集函数
avg（）返回一列的平均值
count（）返回一列的行数
max（） 返回一列的最大那个
min（）不说了
sum（）返回一列的之和
例如返回平均数
MariaDB [CargoWarehouse]> select avg(prod_price) as avg_price
-> from products;
+-----------+
| avg_price |
+-----------+
| 16.133571 |
+-----------+
1 row in set (0.00 sec)
计算客户的总数
MariaDB [CargoWarehouse]> select count(*) as num_cust from customers;
+----------+
| num_cust |
+----------+
| 5 |
+----------+
1 row in set (0.00 sec)
MariaDB [CargoWarehouse]> select
-> count(prod_name) as count,
-> min(prod_price) as min_price,
-> max(prod_price) as max_price,
-> sum(prod_price) as all_price,
-> avg(prod_price) as avg_price
-> from products;
+-------+-----------+-----------+-----------+-----------+
| count | min_price | max_price | all_price | avg_price |
+-------+-----------+-----------+-----------+-----------+
| 14 | 2.50 | 55.00 | 225.87 | 16.133571 |
+-------+-----------+-----------+-----------+-----------+
1 row in set (0.00 sec)
六.分组数据
1.分组
首先试想一下。如果我想查看供货商id为1003都供了几种货。
那么就是
MariaDB [CargoWarehouse]> select count(*) as num_prods
-> from products where vend_id = 1003;
+-----------+
| num_prods |
+-----------+
| 7 |
+-----------+
1 row in set (0.00 sec)
group by
MariaDB [CargoWarehouse]> select vend_id,count(*) as num_prods
-> from products group by vend_id;
+---------+-----------+
| vend_id | num_prods |
+---------+-----------+
| 1001 | 3 |
| 1002 | 2 |
| 1003 | 7 |
| 1005 | 2 |
+---------+-----------+
4 rows in set (0.00 sec)
2.分组选择
以上就是以vend_id为基础分组，那么怎么选择在供货商里供货大于等于3的供货商。
好像有个where可以选择。但在这里不再是where了，这时就是having了。
MariaDB [CargoWarehouse]> select vend_id,count(*) as num_prods
-> from products group by vend_id
-> having count(*) >= 3;
+---------+-----------+
| vend_id | num_prods |
+---------+-----------+
| 1001 | 3 |
| 1003 | 7 |
+---------+-----------+
2 rows in set (0.00 sec)
MariaDB [CargoWarehouse]> select vend_id,sum(prod_price) as vend_price
-> from products
-> group by vend_id;
+---------+------------+
| vend_id | vend_price |
+---------+------------+
| 1001 | 30.97 |
| 1002 | 12.41 |
| 1003 | 92.49 |
| 1005 | 90.00 |
+---------+------------+
4 rows in set (0.00 sec)
3.分组选择过滤group by 和 where相遇
首先看看这种情况出现的时候。
如果我想查看每个供货商提供货物的数量，但那些货物价值小于10美元的货物就算了不统计了，但是提供货物提供的2个以下也不统计。那么怎么查询呢。
MariaDB [CargoWarehouse]> select vend_id,count(*) as num_prods
-> from products
-> where prod_price >= 10
-> group by vend_id
-> having count(*) >= 2
-> order by vend_id desc;
+---------+-----------+
| vend_id | num_prods |
+---------+-----------+
| 1005 | 2 |
| 1003 | 4 |
+---------+-----------+
2 rows in set (0.00 sec)
4.下面检索总计订单价格大于等于50的订单的订单号和总计订单价格
MariaDB [CargoWarehouse]> select order_num,sum(item_price*quantity) as total_price
-> from orderitems
-> group by order_num
-> having sum(item_price*quantity) >= 50;
+-----------+-------------+
| order_num | total_price |
+-----------+-------------+
| 20005 | 149.87 |
| 20006 | 55.00 |
| 20007 | 1000.00 |
| 20008 | 125.00 |
+-----------+-------------+
4 rows in set (0.00 sec)
七.使用子查询
1.使用子查询进行过滤
首先说一下什么情况下使用子查询吧。
比如说我要列出所有订购物品id为TNT2的所有客户。
那么需要注意了，客户的id在orders这个表里，而物品的id在ordersitems这个表里。
来看看表的结构。
MariaDB [CargoWarehouse]> select * from orders;
+-----------+---------------------+---------+
| order_num | order_date | cust_id |
+-----------+---------------------+---------+
| 20005 | 2005-09-01 00:00:00 | 10001 |
| 20006 | 2005-09-12 00:00:00 | 10003 |
| 20007 | 2005-09-30 00:00:00 | 10004 |
| 20008 | 2005-10-03 00:00:00 | 10005 |
| 20009 | 2005-10-08 00:00:00 | 10001 |
+-----------+---------------------+---------+
5 rows in set (0.00 sec)
MariaDB [CargoWarehouse]> select * from orderitems;
+-----------+------------+---------+----------+------------+
| order_num | order_item | prod_id | quantity | item_price |
+-----------+------------+---------+----------+------------+
| 20005 | 1 | ANV01 | 10 | 5.99 |
| 20005 | 2 | ANV02 | 3 | 9.99 |
| 20005 | 3 | TNT2 | 5 | 10.00 |
| 20005 | 4 | FB | 1 | 10.00 |
| 20006 | 1 | JP2000 | 1 | 55.00 |
| 20007 | 1 | TNT2 | 100 | 10.00 |
| 20008 | 1 | FC | 50 | 2.50 |
| 20009 | 1 | FB | 1 | 10.00 |
| 20009 | 2 | OL1 | 1 | 8.99 |
| 20009 | 3 | SLING | 1 | 4.49 |
| 20009 | 4 | ANV03 | 1 | 14.99 |
+-----------+------------+---------+----------+------------+
11 rows in set (0.01 sec)
唯一可以联系这两张表的就是订单号order_num了，只有先查到物品id的订单号，再在
orders这个表通过订单号去查，都有哪些顾客买了物品。
MariaDB [CargoWarehouse]> select cust_id from orders
-> where order_num in
-> (select order_num from orderitems
-> where prod_id = 'TNT2' );
+---------+
| cust_id |
+---------+
| 10001 |
| 10004 |
+---------+
2 rows in set (0.00 sec)
2.作为计算字段的子查询
显示customers表中的每名顾客的订单总数，订单则在orders表中。
先来看看这两张表。
查询方法如下：
先来看看这两张表。
MariaDB [CargoWarehouse]> select * from customers;
+---------+----------------+---------------------+-----------+------------+----------+--------------+--------------+---------------------+
| cust_id | cust_name | cust_address | cust_city | cust_state | cust_zip | cust_country | cust_contact | cust_email |
+---------+----------------+---------------------+-----------+------------+----------+--------------+--------------+---------------------+
| 10001 | Coyote Inc. | 200 Maple Lane | Detroit | MI | 44444 | USA | Y Lee | [email protected] |
| 10002 | Mouse House | 333 Fromage Lane | Columbus | OH | 43333 | USA | Jerry Mouse | NULL |
| 10003 | Wascals | 1 Sunny Place | Muncie | IN | 42222 | USA | Jim Jones | [email protected] |
| 10004 | Yosemite Place | 829 Riverside Drive | Phoenix | AZ | 88888 | USA | Y Sam | [email protected] |
| 10005 | E Fudd | 4545 53rd Street | Chicago | IL | 54545 | USA | E Fudd | NULL |
+---------+----------------+---------------------+-----------+------------+----------+--------------+--------------+---------------------+
5 rows in set (0.00 sec)
MariaDB [CargoWarehouse]> select * from orders;
+-----------+---------------------+---------+
| order_num | order_date | cust_id |
+-----------+---------------------+---------+
| 20005 | 2005-09-01 00:00:00 | 10001 |
| 20006 | 2005-09-12 00:00:00 | 10003 |
| 20007 | 2005-09-30 00:00:00 | 10004 |
| 20008 | 2005-10-03 00:00:00 | 10005 |
| 20009 | 2005-10-08 00:00:00 | 10001 |
+-----------+---------------------+---------+
5 rows in set (0.00 sec)
查询方法如下：
MariaDB [CargoWarehouse]> select cust_name,cust_state,
-> (select count(*)
-> from orders
-> where orders.cust_id = customers.cust_id) as orders
-> from customers
-> order by cust_name;
+----------------+------------+--------+
| cust_name | cust_state | orders |
+----------------+------------+--------+
| Coyote Inc. | MI | 2 |
| E Fudd | IL | 1 |
| Mouse House | OH | 0 |
| Wascals | IN | 1 |
| Yosemite Place | AZ | 1 |
+----------------+------------+--------+
5 rows in set (0.00 sec)
select count(*) from orders where orders.cust_id = customers.cust_idMariaDB [CargoWarehouse]> select count(*) from orders group by cust_id ;
+----------+
| count(*) |
+----------+
| 2 |
| 1 |
| 1 |
| 1 |
+----------+
4 rows in set (0.00 sec)
八.联结表
联结表其实就是一下查好几张表，就是这么简单。
显示编号为20005的订单中的物品。
订单为20005的订单物品有很多信息，如产品名字，供应商，产品价格，数量等等信息。这些信息分别在orderitems，products，vendors。
MariaDB [CargoWarehouse]> select prod_name,vend_name,prod_price,quantity
-> from orderitems,products,vendors
-> where products.vend_id=vendors.vend_id
-> and orderitems.prod_id = products.prod_id
-> and order_num = 20005;
+----------------+-------------+------------+----------+
| prod_name | vend_name | prod_price | quantity |
+----------------+-------------+------------+----------+
| .5 ton anvil | Anvils R Us | 5.99 | 10 |
| 1 ton anvil | Anvils R Us | 9.99 | 3 |
| TNT (5 sticks) | ACME | 10.00 | 5 |
| Bird seed | ACME | 10.00 | 1 |
+----------------+-------------+------------+----------+
4 rows in set (0.00 sec)
九.组合查询
组合查询更简单，就是将两个查询的查询结果合到一起显示了
MariaDB [CargoWarehouse]> select prod_name,prod_price
-> from products where vend_id=1001
-> union
-> select prod_name,prod_price
-> from products where prod_price > 10;
+--------------+------------+
| prod_name | prod_price |
+--------------+------------+
| .5 ton anvil | 5.99 |
| 1 ton anvil | 9.99 |
| 2 ton anvil | 14.99 |
| Detonator | 13.00 |
| JetPack 1000 | 35.00 |
| JetPack 2000 | 55.00 |
| Safe | 50.00 |
+--------------+------------+
7 rows in set (0.00 sec)
十.全文本搜索
这个也很简单，只不过有一点，需要在创建的时候指明FULLTEXT（被查字段）和MyISAM存储引擎。
举个简单的例子。
MariaDB [CargoWarehouse]> select note_text
-> from productnotes
-> where Match(note_text) Against('orange');
+----------------------------------------------------------------------------------------------------------------------+
| note_text |
+----------------------------------------------------------------------------------------------------------------------+
| Quantity varies, sold by the sack load.
All guaranteed to be bright and orange, and suitable for use as rabbit bait. |
+----------------------------------------------------------------------------------------------------------------------+
1 row in set (0.03 sec)