这段时间失业中，刚好在家有大把的时间学习ORACLE和MySQL.顺便也把PHP捡起来。逛逛论坛。
今天论坛上有人问起，刚好写个例子，贴上来。^_^
今天论坛上有人问起，刚好写个例子，贴上来。^_^
init-file 是在MySQL启动的时候加载的脚本。
有两个要注意的。
1. 确保你的mysqld 编译的时候没有加 –disable-grant-options 开关。
2. 确保init-file指定的脚本每行一个具体的语句。
1. 确保你的mysqld 编译的时候没有加 –disable-grant-options 开关。
2. 确保init-file指定的脚本每行一个具体的语句。
使用方法很简单，直接添加到配置文件，比如my.cnf.
添加：
[server] 或者 [mysqld] 或者 [mysqld_safe]
init-file=”Your file location”
[server] 或者 [mysqld] 或者 [mysqld_safe]
init-file=”Your file location”
重启mysqld 就可以看到效果了。
我来做个简单的例子。利用init-file来生成一个CACHE表的数据。
环境： Vbox 虚拟机 Ubuntu 32Bit, MySQL 5.1.30, 启动脚本/home/david/script/control_db
root@david-desktop:/var/log/mysql# /home/david/scripts/control_db enter
Enter password:
…
root@david-desktop:/var/log/mysql# /home/david/scripts/control_db enter
Enter password:
…
mysql> use ytt;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> create table ytt_test ( id int unsigned not null, suffix tinyint unsigned not null, primary key(id,suffix));
Query OK, 0 rows affected (0.00 sec)
mysql> create table ytt_test ( id int unsigned not null, suffix tinyint unsigned not null, primary key(id,suffix));
Query OK, 0 rows affected (0.00 sec)
mysql> insert into ytt_test (id,suffix) values (1,10),(1,20),(1,50),(1,52),(2,55),(2,1),(2,30),
->(2,80),(3,100),(3,22),(3,4),(4,50),(4,20),(4,2),(5,10),(5,90);
Query OK, 16 rows affected (0.00 sec)
Records: 16 Duplicates: 0 Warnings: 0
->(2,80),(3,100),(3,22),(3,4),(4,50),(4,20),(4,2),(5,10),(5,90);
Query OK, 16 rows affected (0.00 sec)
Records: 16 Duplicates: 0 Warnings: 0
简单的CACHE表。
mysql> create table ytt_test_heap engine memory select * from ytt_test where 0;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> create table ytt_test_heap engine memory select * from ytt_test where 0;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
任务就是取到每个分组的最大值。
mysql> select a.* from ytt_test as a where suffix = (select max(suffix) from ytt_test where id = a.id);
+—-+——–+
| id | suffix |
+—-+——–+
| 1 | 52 |
| 2 | 80 |
| 3 | 100 |
| 4 | 50 |
| 5 | 90 |
+—-+——–+
5 rows in set (0.02 sec)
mysql> select a.* from ytt_test as a where suffix = (select max(suffix) from ytt_test where id = a.id);
+—-+——–+
| id | suffix |
+—-+——–+
| 1 | 52 |
| 2 | 80 |
| 3 | 100 |
| 4 | 50 |
| 5 | 90 |
+—-+——–+
5 rows in set (0.02 sec)
然后放到CACHE表中。关于SQL语句优化方面我另外会写的。现在时间多啊。
现在搞init-file
加如下部分到my.cnf
[server]
init-file=/home/david/i.e/init.file
[server]
init-file=/home/david/i.e/init.file
文件/home/david/i.e/init.file 内容很简单，如下：
use ytt;
insert into ytt_test_heap select a.* from ytt_test as a where suffix = (select max(suffix) from ytt_test where id = a.id);
insert into ytt_test_heap select a.* from ytt_test as a where suffix = (select max(suffix) from ytt_test where id = a.id);
给相应的权限。
root@david-desktop:/var/log/mysql# chown -R mysql.mysql /home/david/i.e/init.file
root@david-desktop:/var/log/mysql# chmod 0660 /home/david/i.e/init.file
root@david-desktop:/var/log/mysql# chmod 0660 /home/david/i.e/init.file
然后重启 mysqld.
root@david-desktop:/var/log/mysql# /home/david/scripts/control_db stop
root@david-desktop:/var/log/mysql# /home/david/scripts/control_db start
root@david-desktop:/var/log/mysql# /home/david/scripts/control_db enter
Enter password:
…
mysql> select * from ytt_test_heap;
+—-+——–+
| id | suffix |
+—-+——–+
| 1 | 52 |
| 2 | 80 |
| 3 | 100 |
| 4 | 50 |
| 5 | 90 |
+—-+——–+
5 rows in set (0.00 sec)
root@david-desktop:/var/log/mysql# /home/david/scripts/control_db start
root@david-desktop:/var/log/mysql# /home/david/scripts/control_db enter
Enter password:
…
mysql> select * from ytt_test_heap;
+—-+——–+
| id | suffix |
+—-+——–+
| 1 | 52 |
| 2 | 80 |
| 3 | 100 |
| 4 | 50 |
| 5 | 90 |
+—-+——–+
5 rows in set (0.00 sec)
看到效果了吧。
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