mysql的基本查询命令大全

    本篇博客主要介绍mysql的各种各样的查询命令，关于其他的创建用户，改表的结构就不在这里说了

因为还带了执行结果，所以用目录引索还是方便点

首先看看表的结构

MariaDB [Products]> desc products;
+--------------+--------------+------+-----+---------+-------+
| Field        | Type         | Null | Key | Default | Extra |
+--------------+--------------+------+-----+---------+-------+
| prod_id      | int(11)      | NO   |     | NULL    |       |
| prod_name    | varchar(20)  | NO   |     | NULL    |       |
| prod_price   | float        | NO   |     | NULL    |       |
| prod_country | varchar(2)   | YES  |     | CN      |       |
| vend_id      | int(11)      | YES  |     | NULL    |       |
| prod_desc    | varchar(100) | YES  |     | No desc |       |
+--------------+--------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

再看看表中的内容

MariaDB [Products]> select * from products;
+---------+----------------------+------------+--------------+---------+-----------------------+
| prod_id | prod_name            | prod_price | prod_country | vend_id | prod_desc             |
+---------+----------------------+------------+--------------+---------+-----------------------+
|       1 | snacks               |          2 | CN           |       2 | Delicious cheap       |
|       2 | Mi6                  |       2100 | CN           |       3 | National mobile phone |
|       3 | IPhone7              |       5700 | US           |       2 | Special nouveau riche |
|       4 | Inter Chip           |        200 | US           |       1 | No desc               |
|       5 | Flower               |        2.2 | CN           |       1 | No desc               |
|       6 | U disk               |       92.3 | CN           |       2 | Useful                |
|       7 | Book of nuclear phys |      450.2 | RS           |       3 | reliable              |
|       8 | dog                  |      400.3 | CN           |       3 | Lovely                |
|       9 | Picture              |       20.5 | CN           |       2 | No desc               |
|      10 | Poker                |        2.5 | CN           |       3 | can pass the time     |
+---------+----------------------+------------+--------------+---------+-----------------------+
10 rows in set (0.00 sec)

现在开始介绍查询命令

1.最简单的select语句（检索数据）

检查多个列

MariaDB [Products]> select prod_id,prod_name from products;
+---------+----------------------+
| prod_id | prod_name            |
+---------+----------------------+
|       1 | snacks               |
|       2 | Mi6                  |
|       3 | IPhone7              |
|       4 | Inter Chip           |
|       5 | Flower               |
|       6 | U disk               |
|       7 | Book of nuclear phys |
|       8 | dog                  |
|       9 | Picture              |
|      10 | Poker                |
+---------+----------------------+
10 rows in set (0.00 sec)

检索不同的行

MariaDB [Products]> select distinct vend_id from products;
+---------+
| vend_id |
+---------+
|       2 |
|       3 |
|       1 |
+---------+
3 rows in set (0.00 sec)

限制结果

MariaDB [Products]> select prod_id from products limit 5;
+---------+
| prod_id |
+---------+
|       1 |
|       2 |
|       3 |
|       4 |
|       5 |
+---------+
5 rows in set (0.01 sec)

从第3开始查询，查5行

MariaDB [Products]> select prod_id,prod_name from products limit 3,5;
+---------+----------------------+
| prod_id | prod_name            |
+---------+----------------------+
|       4 | Inter Chip           |
|       5 | Flower               |
|       6 | U disk               |
|       7 | Book of nuclear phys |
|       8 | dog                  |
+---------+----------------------+
5 rows in set (0.00 sec)

2.按顺序输出

从小到大（默认的）

MariaDB [Products]> select prod_name,prod_price from products order by prod_price;
+----------------------+------------+
| prod_name            | prod_price |
+----------------------+------------+
| snacks               |          2 |
| Flower               |        2.2 |
| Poker                |        2.5 |
| Picture              |       20.5 |
| U disk               |       92.3 |
| Inter Chip           |        200 |
| dog                  |      400.3 |
| Book of nuclear phys |      450.2 |
| Mi6                  |       2100 |
| IPhone7              |       5700 |
+----------------------+------------+
10 rows in set (0.00 sec)

从大到小

MariaDB [Products]> select prod_name,prod_price from products order by prod_price desc;
+----------------------+------------+
| prod_name            | prod_price |
+----------------------+------------+
| IPhone7              |       5700 |
| Mi6                  |       2100 |
| Book of nuclear phys |      450.2 |
| dog                  |      400.3 |
| Inter Chip           |        200 |
| U disk               |       92.3 |
| Picture              |       20.5 |
| Poker                |        2.5 |
| Flower               |        2.2 |
| snacks               |          2 |
+----------------------+------------+
10 rows in set (0.00 sec)

给多个列排序（这个不好意思，没效果，假如有3个价格都是2块的，还会对vend_id排序的）

MariaDB [Products]> select prod_name,prod_price,vend_id from products order by prod_price,vend_id desc;
+----------------------+------------+---------+
| prod_name            | prod_price | vend_id |
+----------------------+------------+---------+
| snacks               |          2 |       2 |
| Flower               |        2.2 |       1 |
| Poker                |        2.5 |       3 |
| Picture              |       20.5 |       2 |
| U disk               |       92.3 |       2 |
| Inter Chip           |        200 |       1 |
| dog                  |      400.3 |       3 |
| Book of nuclear phys |      450.2 |       3 |
| Mi6                  |       2100 |       3 |
| IPhone7              |       5700 |       2 |
+----------------------+------------+---------+
10 rows in set (0.00 sec)

3.过滤数据

找出大于100块的物品。

MariaDB [Products]> select prod_name,prod_price from products where prod_price>100;
+----------------------+------------+
| prod_name            | prod_price |
+----------------------+------------+
| Mi6                  |       2100 |
| IPhone7              |       5700 |
| Inter Chip           |        200 |
| Book of nuclear phys |      450.2 |
| dog                  |      400.3 |
+----------------------+------------+
5 rows in set (0.00 sec)

LIKE 通配符过滤

MariaDB [Products]> select prod_id,prod_desc from products where prod_desc like 'No%';
+---------+-----------+
| prod_id | prod_desc |
+---------+-----------+
|       4 | No desc   |
|       5 | No desc   |
|       9 | No desc   |
+---------+-----------+
3 rows in set (0.00 sec)

like 还是很low的。其中%代表任何字符出现任何次数。_代表的是匹配一个字符
下面说的是更强大的regexp可以匹配只要有这个单词就匹配。跟grep有点像

MariaDB [Products]> select prod_id,prod_desc from products where prod_desc regexp 'No';
+---------+-----------------------+
| prod_id | prod_desc             |
+---------+-----------------------+
|       3 | Special nouveau riche |
|       4 | No desc               |
|       5 | No desc               |
|       9 | No desc               |
+---------+-----------------------+
4 rows in set (0.00 sec)

这里的匹配就和shell脚本里的的正则表达式就很像似了（\\就是\转移）

MariaDB [Products]> select prod_id,prod_price from products where  prod_price regexp '\\.';
+---------+------------+
| prod_id | prod_price |
+---------+------------+
|       5 |        2.2 |
|       6 |       92.3 |
|       7 |      450.2 |
|       8 |      400.3 |
|       9 |       20.5 |
|      10 |        2.5 |
+---------+------------+
6 rows in set (0.00 sec)

小结一下，[123]表示1,2,3都有可能出现一次 或者 1|2|3
而[^123]就是不可能是1,2,3中的一个。^和$就是表示可能开头和结尾是什么。是不是和shell一模一样呢。对了还有[:alnum:]等等用法和.代表任意一个字符。?匹配前面的字符出现0,1次.+代表前面的字符出现1或者多次。*代表匹配0到多次。

MariaDB [Products]> select prod_id,prod_price from products where  prod_price regexp '[[:digit:]]{4}';
+---------+------------+
| prod_id | prod_price |
+---------+------------+
|       2 |       2100 |
|       3 |       5700 |
+---------+------------+
2 rows in set (0.00 sec)

4.创建计算字段

为了演示这个我再创建一列

MariaDB [Products]> alter table products add prod_num int NOT NULL after prod_price;
Query OK, 10 rows affected (0.15 sec)
Records: 10  Duplicates: 0  Warnings: 0

创建两个列合成一个列输出

MariaDB [Products]> select Concat(prod_name,'(',prod_country,')') as prod_title from products order by prod_name;
+--------------------------+
| prod_title               |
+--------------------------+
| Book of nuclear phys(RS) |
| dog(CN)                  |
| Flower(CN)               |
| Inter Chip(US)           |
| IPhone7(US)              |
| Mi6(CN)                  |
| Picture(CN)              |
| Poker(CN)                |
| snacks(CN)               |
| U disk(CN)               |
+--------------------------+
10 rows in set (0.00 sec)

使用Concat和并列，并用as起个别名。其实as是很实用的一个命令。

使用算数查找，个计算产品单价和产品个数的乘积。而且本来并不存在产品总价这列

MariaDB [Products]> select prod_name,prod_price,prod_num,prod_price*prod_num as item_price from products ;
+----------------------+------------+----------+--------------------+
| prod_name            | prod_price | prod_num | item_price         |
+----------------------+------------+----------+--------------------+
| snacks               |          2 |        1 |                  2 |
| Mi6                  |       2100 |       23 |              48300 |
| IPhone7              |       5700 |        2 |              11400 |
| Inter Chip           |        200 |        2 |                400 |
| Flower               |        2.2 |        4 |  8.800000190734863 |
| U disk               |       92.3 |        7 |  646.1000213623047 |
| Book of nuclear phys |      450.2 |       18 | 8103.6002197265625 |
| dog                  |      400.3 |       20 |  8005.999755859375 |
| Picture              |       20.5 |        0 |                  0 |
| Poker                |        2.5 |        7 |               17.5 |
+----------------------+------------+----------+--------------------+
10 rows in set (0.00 sec)

后面的那个是因为flout类型的

5.使用函数

使用mysql的函数。

MariaDB [Products]> select upper(prod_name) from products;
+----------------------+
| upper(prod_name)     |
+----------------------+
| SNACKS               |
| MI6                  |
| IPHONE7              |
| INTER CHIP           |
| FLOWER               |
| U DISK               |
| BOOK OF NUCLEAR PHYS |
| DOG                  |
| PICTURE              |
| POKER                |
+----------------------+
10 rows in set (0.00 sec)

还有soundex（）匹配发音类似的单词。
还有专门和日期和时间匹配的处理函数

AddDate()   增加一个日期
AddTime()   增加一个时间
Date_Add()   高度灵活的日期运算函数

CurDate()    返回当前日期
CurTime()    返回当前时间
Now()          返回当前日期和时间

DateDiff()     返回2个日期之差
Date_Format()  返回一个格式化的日期或时间串
Day()                返回日期中的天数
DayOfWeek()   返回日期中的星期
Hour()               返回日期中的小时部分
Minute()            返回日期中的分钟部分
Month()            返回日期中的月份部分
Second()          返回日期中的秒数部分
Time()              返回日期中的时间部分
Date()              返回日期中的日期部分

Year()              返回日期中的年份部分

MariaDB [Products]> select upper(prod_name),Now() as Time  from products;
+----------------------+---------------------+
| upper(prod_name)     | Time                |
+----------------------+---------------------+
| SNACKS               | 2016-12-01 10:29:46 |
| MI6                  | 2016-12-01 10:29:46 |
| IPHONE7              | 2016-12-01 10:29:46 |
| INTER CHIP           | 2016-12-01 10:29:46 |
| FLOWER               | 2016-12-01 10:29:46 |
| U DISK               | 2016-12-01 10:29:46 |
| BOOK OF NUCLEAR PHYS | 2016-12-01 10:29:46 |
| DOG                  | 2016-12-01 10:29:46 |
| PICTURE              | 2016-12-01 10:29:46 |
| POKER                | 2016-12-01 10:29:46 |
+----------------------+---------------------+

AVG()    返回某列的平均值
COUNT()   返回某列的行数
MAX()     返回某列的最大值
MIN()      返回某列的最小值
SUM()    返回某列的总和

MariaDB [Products]> select AVG(prod_price) as average  from products;
+-------------------+
| average           |
+-------------------+
| 897.0000003099442 |
+-------------------+
1 row in set (0.00 sec)