mysql学习-sql根本使用

mysql学习--sql基本使用 上图为数据库操作分类： 以下的操作参考（mysql必知必会） 创建数据库 执行脚本建表： mysql create database mytest;Query OK, 1 row affected (0.07 sec)mysql show databases;+--------------------+| Database |+----------------

上图为数据库操作分类：

以下的操作参考（mysql必知必会）

创建数据库 执行脚本建表：

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)

删除重复行：

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：

mysql> select prod_name from products
    -> limit 5;
+--------------+
| prod_name    |
+--------------+
| .5 ton anvil |
| 1 ton anvil  |
| 2 ton anvil  |
| Detonator    |
| Bird seed    |
+--------------+
5 rows in set (0.00 sec)

 从第5行开始的5行：

mysql> select prod_name
    -> from products
    -> limit 5,5;
+--------------+
| prod_name    |
+--------------+
| Carrots      |
| Fuses        |
| JetPack 1000 |
| JetPack 2000 |
| Oil can      |
+--------------+
5 rows in set (0.00 sec)

order by 子句对一个或者多个列进行输出排序：

mysql> select prod_name
    -> from products
    -> order by prod_name;
+----------------+
| prod_name      |
+----------------+
| .5 ton anvil   |
| 1 ton anvil    |
| 2 ton anvil    |
| Bird seed      |
| Carrots        |
| Detonator      |
| Fuses          |
| JetPack 1000   |
| JetPack 2000   |
| Oil can        |
| Safe           |
| Sling          |
| TNT (1 stick)  |
| TNT (5 sticks) |
+----------------+

首先按price排序，只有price相同时，才按照名称排序：

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DESC关键字：

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          |