MySQL mod 后全部是偶数

1、MySQL在DOS窗口进入

    1）设置环境变量：Path添加MySQL运行路径（C:\Program Files\MySQL\MySQL Server 5.7\bin）

mysql -u root -p  cms -h 127.0.0.1 -P 3306

2、show命令

show databases; //显示所有数据库
use cms; //进入某个数据库
show tables; //显示某个数据库下的所有表
 
describe t_admin;
show columns from t_admin; //显示某张表下的所有列字段信息
 
show status; //显示服务器状态信息
show create database database_name; //显示创建数据库的语句
show create table table_name form database db_name; //显示创建表的语句
show grants; //显示授予用户的安全权限
show errors; //显示服务器错误信息
show warnings; //显示服务器警告消息
show databases; //显示所有数据库
use cms; //进入某个数据库
show tables; //显示某个数据库下的所有表
 
describe t_admin;
show columns from t_admin; //显示某张表下的所有列字段信息
 
show status; //显示服务器状态信息
show create database database_name; //显示创建数据库的语句
show create table table_name form database db_name; //显示创建表的语句
show grants; //显示授予用户的安全权限
show errors; //显示服务器错误信息
show warnings; //显示服务器警告消息

3、检索列通配符使用规则：除非你确实需要使用表中的所有列，否则最好不用使用【*】通配符，这样检索不需要的列会降低检索和应用程序的性能

4、distinct：去除重复（SELECT DISTINCT 列名称, 列名称 FROM 表名称）

select distinct name from A // 对字段name去重
select distinct id, name from A // 对字段id、name合集去重
select distinct name from A // 对字段name去重
select distinct id, name from A // 对字段id、name合集去重

5、limit：限制结果：默认从第0行开始

select prod_name from products limit 5; // 从第0行开始，取出五行记录
select prod_name from products limit 5, 5 //从第5行开始，取出5行记录
select * from t_activity_order limit 4 offset 3; //从第3行开始，取出4行记录 == select * from t_activity_order limit 3, 4
select prod_name from products limit 5; // 从第0行开始，取出五行记录
select prod_name from products limit 5, 5 //从第5行开始，取出5行记录
select * from t_activity_order limit 4 offset 3; //从第3行开始，取出4行记录 == select * from t_activity_order limit 3, 4

6、空值NULL检查：在过滤中选择不具有特定值的行时，可能希望返回具有NULL值的行，但是不行，因为未知具有特殊的含义，数据库不知道它们是否匹配，所以在匹配过滤或者不匹配过滤的时候不返回它们

select * from t_admin where name != 'admin' //返回所有name不为admin的列，但如果name列中如果存在NULL的行，则不会返回
select * from t_admin where name != 'admin' //返回所有name不为admin的列，但如果name列中如果存在NULL的行，则不会返回

7、通配符：like

    %：代表任意字符（包含0-无穷个）

    _：代表一个字符

通配符使用原则：1）不要过度使用通配符，搜索效率很低。如果其他操作符能达到相同的目的，应该使用其他操作符

                          2）避免将通配符放在搜索条件的开始处，这样搜索起来最慢

8、正则表达式：字段 regexp '正则表达式'

• regexp和like区别：like是整行匹配，regexp是对行内的内容进行匹配
• regexp匹配不区分大小写，如果需要区分大小写，使用regxrep binary关键字

    正则匹配规则：

    1）. ：匹配任意一个字符

    2）| ：直接or操作（1|2|3匹配1或者2或者3）

[]：匹配几个字符中的一个（[1-578]匹配1、2、3、4、5、7、8中的一个）发现使用[123]和(1|2|3)和[1|2|3]作用一样

    4）^：如果在开始位置，表示匹配以其后面字符为开始，如果在中间表示非

    5）-：[a-zA-Z0-9]

    6）匹配特殊字符：前面加\\

    7）*：匹配0个或者多个

等价于{1,}）

    9）?：匹配0个或者1个（等价于{0,1}）

  10）{n}：指定n个数目的匹配

  11）{n, }：指定不少于指定数目的匹配

  12）{n,m}：匹配数目的范围（m不超过255）

  13）$：文本的结尾

  14）[[:<:]]：词的开始

  15）[[:>:]]：词的结尾

mysql> select prod_id, prod_name from products where prod_name regexp '.000';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| JP1000  | JetPack 1000 |
| JP2000  | JetPack 2000 |
+---------+--------------+
2 rows in set (0.08 sec)

mysql> select prod_id, prod_name from products where prod_name regexp 'detonator';
+---------+-----------+
| prod_id | prod_name |
+---------+-----------+
| DTNTR   | Detonator |
+---------+-----------+
1 row in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp binary 'detonator';
Empty set (0.04 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '1000|2000|3000';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| JP1000  | JetPack 1000 |
| JP2000  | JetPack 2000 |
+---------+--------------+
2 rows in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '[123] ton';
+---------+-------------+
| prod_id | prod_name   |
+---------+-------------+
| ANV02   | 1 ton anvil |
| ANV03   | 2 ton anvil |
+---------+-------------+
2 rows in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '[^123] ton';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| ANV01   | .5 ton anvil |
+---------+--------------+
1 row in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '(1|2|3) ton';
+---------+-------------+
| prod_id | prod_name   |
+---------+-------------+
| ANV02   | 1 ton anvil |
| ANV03   | 2 ton anvil |
+---------+-------------+
2 rows in set (0.00 sec)

mysql> select prod_id,note_date from productnotes where note_date regexp '2005-0(8|9)-[01]';
+---------+---------------------+
| prod_id | note_date           |
+---------+---------------------+
| TNT2    | 2005-08-17 00:00:00 |
| OL1     | 2005-08-18 00:00:00 |
| SAFE    | 2005-08-18 00:00:00 |
| FC      | 2005-08-19 00:00:00 |
| ANV03   | 2005-09-01 00:00:00 |
| FC      | 2005-09-01 00:00:00 |
| SLING   | 2005-09-02 00:00:00 |
| SAFE    | 2005-09-02 00:00:00 |
| ANV01   | 2005-09-05 00:00:00 |
| SAFE    | 2005-09-07 00:00:00 |
+---------+---------------------+
10 rows in set (0.00 sec)

mysql> select * from vendors where vend_name regexp '\\.';
+---------+--------------+-----------------+-----------+------------+----------+--------------+
| vend_id | vend_name    | vend_address    | vend_city | vend_state | vend_zip | vend_country |
+---------+--------------+-----------------+-----------+------------+----------+--------------+
|    1004 | Furball Inc. | 1000 5th Avenue | New York  | NY         | 11111    | USA          |
+---------+--------------+-----------------+-----------+------------+----------+--------------+
1 row in set (0.00 sec)

mysql> select * from products where prod_name regexp '\\([0-9] stick?\\)';
+---------+---------+---------------+------------+------------------------+
| prod_id | vend_id | prod_name     | prod_price | prod_desc              |
+---------+---------+---------------+------------+------------------------+
| TNT1    |    1003 | TNT (1 stick) |       2.50 | TNT, red, single stick |
+---------+---------+---------------+------------+------------------------+
1 row in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '[0-9]{4}';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| JP1000  | JetPack 1000 |
| JP2000  | JetPack 2000 |
+---------+--------------+
2 rows in set (0.00 sec)
或者
mysql> select prod_id, prod_name from products where prod_name regexp '[0-9][0-9][0-9][0-9]';

mysql> select prod_id, prod_name from products where prod_name regexp '^[0-9\\.]';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| ANV01   | .5 ton anvil |
| ANV02   | 1 ton anvil  |
| ANV03   | 2 ton anvil  |
+---------+--------------+
3 rows in set (0.00 sec)
mysql> select prod_id, prod_name from products where prod_name regexp '.000';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| JP1000  | JetPack 1000 |
| JP2000  | JetPack 2000 |
+---------+--------------+
2 rows in set (0.08 sec)

mysql> select prod_id, prod_name from products where prod_name regexp 'detonator';
+---------+-----------+
| prod_id | prod_name |
+---------+-----------+
| DTNTR   | Detonator |
+---------+-----------+
1 row in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp binary 'detonator';
Empty set (0.04 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '1000|2000|3000';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| JP1000  | JetPack 1000 |
| JP2000  | JetPack 2000 |
+---------+--------------+
2 rows in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '[123] ton';
+---------+-------------+
| prod_id | prod_name   |
+---------+-------------+
| ANV02   | 1 ton anvil |
| ANV03   | 2 ton anvil |
+---------+-------------+
2 rows in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '[^123] ton';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| ANV01   | .5 ton anvil |
+---------+--------------+
1 row in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '(1|2|3) ton';
+---------+-------------+
| prod_id | prod_name   |
+---------+-------------+
| ANV02   | 1 ton anvil |
| ANV03   | 2 ton anvil |
+---------+-------------+
2 rows in set (0.00 sec)

mysql> select prod_id,note_date from productnotes where note_date regexp '2005-0(8|9)-[01]';
+---------+---------------------+
| prod_id | note_date           |
+---------+---------------------+
| TNT2    | 2005-08-17 00:00:00 |
| OL1     | 2005-08-18 00:00:00 |
| SAFE    | 2005-08-18 00:00:00 |
| FC      | 2005-08-19 00:00:00 |
| ANV03   | 2005-09-01 00:00:00 |
| FC      | 2005-09-01 00:00:00 |
| SLING   | 2005-09-02 00:00:00 |
| SAFE    | 2005-09-02 00:00:00 |
| ANV01   | 2005-09-05 00:00:00 |
| SAFE    | 2005-09-07 00:00:00 |
+---------+---------------------+
10 rows in set (0.00 sec)

mysql> select * from vendors where vend_name regexp '\\.';
+---------+--------------+-----------------+-----------+------------+----------+--------------+
| vend_id | vend_name    | vend_address    | vend_city | vend_state | vend_zip | vend_country |
+---------+--------------+-----------------+-----------+------------+----------+--------------+
|    1004 | Furball Inc. | 1000 5th Avenue | New York  | NY         | 11111    | USA          |
+---------+--------------+-----------------+-----------+------------+----------+--------------+
1 row in set (0.00 sec)

mysql> select * from products where prod_name regexp '\\([0-9] stick?\\)';
+---------+---------+---------------+------------+------------------------+
| prod_id | vend_id | prod_name     | prod_price | prod_desc              |
+---------+---------+---------------+------------+------------------------+
| TNT1    |    1003 | TNT (1 stick) |       2.50 | TNT, red, single stick |
+---------+---------+---------------+------------+------------------------+
1 row in set (0.00 sec)

mysql> select prod_id, prod_name from products where prod_name regexp '[0-9]{4}';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| JP1000  | JetPack 1000 |
| JP2000  | JetPack 2000 |
+---------+--------------+
2 rows in set (0.00 sec)
或者
mysql> select prod_id, prod_name from products where prod_name regexp '[0-9][0-9][0-9][0-9]';

mysql> select prod_id, prod_name from products where prod_name regexp '^[0-9\\.]';
+---------+--------------+
| prod_id | prod_name    |
+---------+--------------+
| ANV01   | .5 ton anvil |
| ANV02   | 1 ton anvil  |
| ANV03   | 2 ton anvil  |
+---------+--------------+
3 rows in set (0.00 sec)

9、可以在不使用数据库表的情况下，检查正则表达式是否正确，返回结果如果为0，则表示不匹配，如果返回1则表示匹配

mysql> select '中文' regexp '[0-9]';
+-------------------------+
| '中文' regexp '[0-9]'   |
+-------------------------+
|                       0 |
+-------------------------+
1 row in set (0.00 sec)

mysql> select '123wqwww' regexp '[0-9]';
+---------------------------+
| '123wqwww' regexp '[0-9]' |
+---------------------------+
|                         1 |
+---------------------------+
1 row in set (0.00 sec)
mysql> select '中文' regexp '[0-9]';
+-------------------------+
| '中文' regexp '[0-9]'   |
+-------------------------+
|                       0 |
+-------------------------+
1 row in set (0.00 sec)

mysql> select '123wqwww' regexp '[0-9]';
+---------------------------+
| '123wqwww' regexp '[0-9]' |
+---------------------------+
|                         1 |
+---------------------------+
1 row in set (0.00 sec)

10、拼接字段

    1）将值联接到一起形成单个值，在MySQL中使用concat()函数

mysql> select concat(vend_name, '(', vend_country, ')') from vendors;
+-------------------------------------------+
| concat(vend_name, '(', vend_country, ')') |
+-------------------------------------------+
| Anvils R Us(USA)                          |
| LT Supplies(USA)                          |
| ACME(USA)                                 |
| Furball Inc.(USA)                         |
| Jet Set(England)                          |
| Jouets Et Ours(France)                    |
+-------------------------------------------+
6 rows in set (0.00 sec)
mysql> select concat(vend_name, '(', vend_country, ')') from vendors;
+-------------------------------------------+
| concat(vend_name, '(', vend_country, ')') |
+-------------------------------------------+
| Anvils R Us(USA)                          |
| LT Supplies(USA)                          |
| ACME(USA)                                 |
| Furball Inc.(USA)                         |
| Jet Set(England)                          |
| Jouets Et Ours(France)                    |
+-------------------------------------------+
6 rows in set (0.00 sec)

    2）rtrim()、ltrim()、trim()：去掉左右空格

mysql> select concat(rtrim(vend_name), '(', ltrim(vend_country), ')') from vendors;
+---------------------------------------------------------+
| concat(rtrim(vend_name), '(', ltrim(vend_country), ')') |
+---------------------------------------------------------+
| Anvils R Us(USA)                                        |
| LT Supplies(USA)                                        |
| ACME(USA)                                               |
| Furball Inc.(USA)                                       |
| Jet Set(England)                                        |
| Jouets Et Ours(France)                                  |
+---------------------------------------------------------+
mysql> select concat(rtrim(vend_name), '(', ltrim(vend_country), ')') from vendors;
+---------------------------------------------------------+
| concat(rtrim(vend_name), '(', ltrim(vend_country), ')') |
+---------------------------------------------------------+
| Anvils R Us(USA)                                        |
| LT Supplies(USA)                                        |
| ACME(USA)                                               |
| Furball Inc.(USA)                                       |
| Jet Set(England)                                        |
| Jouets Et Ours(France)                                  |
+---------------------------------------------------------+

    3）使用别名：as

mysql> select concat(vend_name, '(', vend_country, ')') as vend_title from vendors;
+------------------------+
| vend_title             |
+------------------------+
| Anvils R Us(USA)       |
| LT Supplies(USA)       |
| ACME(USA)              |
| Furball Inc.(USA)      |
| Jet Set(England)       |
| Jouets Et Ours(France) |
+------------------------+
6 rows in set (0.00 sec)
mysql> select concat(vend_name, '(', vend_country, ')') as vend_title from vendors;
+------------------------+
| vend_title             |
+------------------------+
| Anvils R Us(USA)       |
| LT Supplies(USA)       |
| ACME(USA)              |
| Furball Inc.(USA)      |
| Jet Set(England)       |
| Jouets Et Ours(France) |
+------------------------+
6 rows in set (0.00 sec)

    4）执行算术运算：+-*/

mysql> 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 (0.01 sec)

mysql> select now();
+---------------------+
| now()               |
+---------------------+
| 2015-04-20 22:54:25 |
+---------------------+
1 row in set (0.00 sec)
mysql> 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 (0.01 sec)

mysql> select now();
+---------------------+
| now()               |
+---------------------+
| 2015-04-20 22:54:25 |
+---------------------+
1 row in set (0.00 sec)