mysql学习--mysql必知必会

上图为数据库操作分类：

下面的操作參考（mysql必知必会）

创建数据库运行脚本建表：

mysql> create database mytest;

Query OK, 1 row affected (0.07 sec)

mysql> show databases;

+--------------------+

| Database           |

+--------------------+

| information_schema |

| mysql              |

| mytest             |

| performance_schema |

+--------------------+

4 rows in set (0.00 sec)

mysql> use myte

ERROR 1049 (42000): Unknown database 'myte'

mysql> use mytest;

Database changed

mysql> show tables;

Empty set (0.00 sec)

mysql> source /home/huangcd/mysql_scripts/create.sql

mysql> source /home/huangcd/mysql_scripts/populate.sql

mysql> show tables;

+------------------+

| Tables_in_mytest |

+------------------+

| customers        |

| orderitems       |

| orders           |

| productnotes     |

| products         |

| vendors          |

+------------------+

6 rows in set (0.02 sec)

删除反复行：

mysql> select vend_id from products;
+---------+
| vend_id |
+---------+
|    1001 |
|    1001 |
|    1001 |
|    1002 |
|    1002 |
|    1003 |
|    1003 |
|    1003 |
|    1003 |
|    1003 |
|    1003 |
|    1003 |
|    1005 |
|    1005 |
+---------+
14 rows in set (0.00 sec)

mysql> select distinct vend_id from products;
+---------+
| vend_id |
+---------+
|    1001 |
|    1002 |
|    1003 |
|    1005 |
+---------+
4 rows in set (0.04 sec)

返回结果中不多于5行：

从第5行開始的5行：

order by 子句对一个或者多个列进行输出排序：

首先按price排序，仅仅有price同样时，才依照名称排序：

mysql> select prod_id, prod_price, prod_name
    -> from products
    -> order by prod_price, prod_name;
+---------+------------+----------------+
| prod_id | prod_price | prod_name      |
+---------+------------+----------------+
| FC      |       2.50 | Carrots        |
| TNT1    |       2.50 | TNT (1 stick) |
| FU1     |       3.42 | Fuses          |
| SLING   |       4.49 | Sling          |
| ANV01   |       5.99 | .5 ton anvil   |
| OL1     |       8.99 | Oil can        |
| ANV02   |       9.99 | 1 ton anvil    |
| FB      |      10.00 | Bird seed      |
| TNT2    |      10.00 | TNT (5 sticks) |
| DTNTR   |      13.00 | Detonator      |
| ANV03   |      14.99 | 2 ton anvil    |
| JP1000 |      35.00 | JetPack 1000   |
| SAFE    |      50.00 | Safe           |
| JP2000 |      55.00 | JetPack 2000   |
+---------+------------+----------------+
14 rows in set (0.05 sec)

默认排序方式是升序，若用降序必须用DESCkeyword：

mysql> select prod_id, prod_price, prod_name from products order by prod_price DESC;
+---------+------------+----------------+
| 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) |
| FB      |      10.00 | Bird seed      |
| ANV02   |       9.99 | 1 ton anvil    |
| OL1     |       8.99 | Oil can        |
| ANV01   |       5.99 | .5 ton anvil   |
| SLING   |       4.49 | Sling          |
| FU1     |       3.42 | Fuses          |
| FC      |       2.50 | Carrots        |
| TNT1    |       2.50 | TNT (1 stick) |
+---------+------------+----------------+
14 rows in set (0.02 sec)

mysql> select prod_id, prod_price, prod_name from products order by prod_price DESC, prod_name;
+---------+------------+----------------+
| 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      |
| FB      |      10.00 | Bird seed      |
| TNT2    |      10.00 | TNT (5 sticks) |
| ANV02   |       9.99 | 1 ton anvil    |
| OL1     |       8.99 | Oil can        |
| ANV01   |       5.99 | .5 ton anvil   |
| SLING   |       4.49 | Sling          |
| FU1     |       3.42 | Fuses          |

价格最高的一个：

mysql> select prod_price

    -> from products

    -> order by prod_price desc

    -> limit 1;

+------------+

| prod_price |

+------------+

|      55.00 |

+------------+

1 row in set (0.12 sec)

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mysql> select prod_name, prod_price

    -> from products

    -> where prod_price between 5 and 10;

+----------------+------------+

| prod_name      | prod_price |

+----------------+------------+

| .5 ton anvil   |       5.99 |

| 1 ton anvil    |       9.99 |

| Bird seed      |      10.00 |

| Oil can        |       8.99 |

| TNT (5 sticks) |      10.00 |

+----------------+------------+

5 rows in set (0.09 sec)

空值检查：

mysql> select prod_name

    -> from products

    -> where prod_price is null;

Empty set (0.01 sec)

mysql> select cust_id

    -> from customers

    -> where cust_email is null;

+---------+

| cust_id |

+---------+

|   10002 |

|   10005 |

+---------+

2 rows in set (0.00 sec)

or操作符：

mysql> select prod_name,prod_price from products where vend_id =1002 or vend_id = 1003;

+----------------+------------+

| prod_name      | prod_price |

+----------------+------------+

| Detonator      |      13.00 |

| Bird seed      |      10.00 |

| Carrots        |       2.50 |

| Fuses          |       3.42 |

| Oil can        |       8.99 |

| Safe           |      50.00 |

| Sling          |       4.49 |

| TNT (1 stick)  |       2.50 |

| TNT (5 sticks) |      10.00 |

+----------------+------------+

9 rows in set (0.05 sec)

in操作符：

mysql> select prod_name, prod_price

    -> from products

    -> where vend_id in (1002, 1003)

    -> order by prod_name;

+----------------+------------+

| prod_name      | prod_price |

+----------------+------------+

| Bird seed      |      10.00 |

| Carrots        |       2.50 |

| Detonator      |      13.00 |

| Fuses          |       3.42 |

| Oil can        |       8.99 |

| Safe           |      50.00 |

| Sling          |       4.49 |

| TNT (1 stick)  |       2.50 |

| TNT (5 sticks) |      10.00 |

+----------------+------------+

9 rows in set (0.07 sec)

in最大的长处是能够包括其它select子句。

not操作符：

mysql> select prod_name, prod_price

    -> from products

    -> where vend_id not in (1002, 1003)

    -> order by prod_name;

+--------------+------------+

| prod_name    | prod_price |

+--------------+------------+

| .5 ton anvil |       5.99 |

| 1 ton anvil  |       9.99 |

| 2 ton anvil  |      14.99 |

| JetPack 1000 |      35.00 |

| JetPack 2000 |      55.00 |

+--------------+------------+

5 rows in set (0.00 sec)

在搜索子句中使用通配符，必须使用like操作符。like指示后跟的搜索模式是通配符而不是直接相等匹配。

%通配符：随意字符出现随意次数

mysql> 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 (0.05 sec)

mysql> select prod_id, prod_name from products where prod_name like '%anvil%';

+---------+--------------+

| prod_id | prod_name    |

+---------+--------------+

| ANV01   | .5 ton anvil |

| ANV02   | 1 ton anvil  |

| ANV03   | 2 ton anvil  |

+---------+--------------+

3 rows in set (0.00 sec)

_通配符：匹配随意单个字符

mysql> select prod_id, prod_name from products where prod_name like '_ton anvil';

Empty set (0.00 sec)

mysql> 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)

mysql必知必会前八章如上。