查詢數據

Question

有在不同服務器上的兩個不同的數據庫兩種觀點，我要加入他們的行列，使幾個疑問。

我有什麼選擇？

我該怎麼辦？

加入的觀點在同一個數據庫工作。

SELECT * FROM view1 
UNION ALL 
SELECT * FROM view2 

感謝

Answer 1

你可以在MySQL中使用聯合功能。

1. 在你的MySQL啓用聯合

登錄到MySQL的CLI以root（或具有足夠權限的另一個帳戶）。

類型：show engines; 你應該看不到任何聯邦引擎在這一點上，像這樣：

mysql> show engines; 
+------------+---------+------------------------------------------------------------+--- -----------+------+------------+ 
| Engine  | Support | Comment             | Transactions | XA | Savepoints | 
+------------+---------+------------------------------------------------------------+--- -----------+------+------------+ 
| MRG_MYISAM | YES  | Collection of identical MyISAM tables      | NO    | NO | NO   | 
| CSV  | YES  | CSV storage engine           | NO   | NO | NO   | 
| MyISAM  | DEFAULT | Default engine as of MySQL 3.23 with great performance  | NO   | NO | NO   | 
| InnoDB  | YES  | Supports transactions, row-level locking, and foreign keys | YES   | YES | YES  | 
| MEMORY  | YES  | Hash based, stored in memory, useful for temporary tables | NO   | NO | NO   | 
+------------+---------+------------------------------------------------------------+--------------+------+------------+ 
5 rows in set (0.00 sec) 

爲了使盟員引擎，鍵入以下內容：

install plugin federated soname 'ha_federated.so'; 

不介意，如果你得到ERROR 1125（HY000）：功能「聯合」已存在

現在可以行「聯合」安全地添加到/etc/my.cnf文件裏是這樣的：

[mysqld] 
datadir=/var/lib/mysql 
socket=/var/lib/mysql/mysql.sock 
user=mysql 
# Disabling symbolic-links is recommended to prevent assorted security risks 
symbolic-links=0 
federated 

[mysqld_safe] 
log-error=/var/log/mysqld.log 
pid-file=/var/run/mysqld/mysqld.pid 

重新啓動mysqld（服務mysqld restart等）

重新啓動後，請回到mysql CLI。

類型'show engines;' 您現在應該看到FEDERATED引擎可用，並且支持爲YES。

mysql> show engines; 
+------------+---------+------------------------------------------------------------+--------------+------+------------+ 
| Engine  | Support | Comment             | Transactions | XA | Savepoints | 
+------------+---------+------------------------------------------------------------+--------------+------+------------+ 
| FEDERATED | YES  | Federated MySQL storage engine        | NO   | NO | NO   | 
| CSV  | YES  | CSV storage engine           | NO   | NO | NO   | 
| MyISAM  | DEFAULT | Default engine as of MySQL 3.23 with great performance  | NO   | NO | NO   | 
| InnoDB  | YES  | Supports transactions, row-level locking, and foreign keys | YES   | YES | YES  | 
| MEMORY  | YES  | Hash based, stored in memory, useful for temporary tables | NO   | NO | NO   | 
| MRG_MYISAM | YES  | Collection of identical MyISAM tables      | NO   | NO | NO   | 
+------------+---------+------------------------------------------------------------+--------------+------+------------+ 
6 rows in set (0.00 sec) 

重啓MySQL

service mysqld status 
service mysqld stop 
service mysqld start 

在DB2

在DB1中創建DB1和視圖2廠景，

CREATE table federated_table (
id int not null, 
name VARCHAR(32) NOT NULL DEFAULT '' 
) 
ENGINE=FEDERATED 

CONNECTION='mysql://user_name:password@remote_server_name:3306/db2/view2'; 

注federated_table和view2必須使用相同的列名稱並鍵入

執行SELECT * FROM db2.federated_table;

執行select * from db1.view1 union all select * FROM db1.federated_table;

參見：http://eves4code.blogspot.in/2015/12/querying-data-by-joining-two-views-in.html