In the previous post, we have seen a basic theory and configuration of FEDERATED table. In this post, I am going to create a FEDERATED table which is used to SELECT data from another MySQL Server.

How to create FEDERATED Tables?

Assume that we have two running servers, either both on the same host or different hosts.

For example:

Server – A108 (Remote MySQL Server)
Server – B108 (Local MySQL Server)

We need to execute the SELECT command from Server B108 and fetching data from Server A108.
Here, Server A108 is a remote server and Server B108 is a local server.

Now create a sample table in Server A108.

CREATE TABLE tbl_RemoteTable 
(
    ID integer
    ,Name VARCHAR(255)
) 
ENGINE=InnoDB;

Now, create a FEDERATED table in Server B108 to SELECT data from Server A108.
You have to specify FEDERATED engine with remote CONNECTION information.

CREATE TABLE tbl_RemoteTable 
(
    ID integer
    ,Name VARCHAR(255)
) 
ENGINE=FEDERATED
CONNECTION='mysql://root:root@localhost:3306/B108/tbl_RemoteTable';

As you can see, I created FEDERATED table into Local Server B108 using the connection information of Remote Server A108.

You can access this table like any other table, and if any data insert or delete in remote Table, it automatically updates here because this is a virtual table.

Below are different format of connection strings:

CONNECTION='mysql://username:password@hostname:port/database/tablename'
CONNECTION='mysql://username@hostname/database/tablename'
CONNECTION='mysql://username:password@hostname/database/tablename'

MySQL – ERROR 1130: Host is not allowed to connect to this MySQL server.

I got the above error when one of my client machines were accessing MySQL Server.
By default, MySQL does not allow the remote client to connect the MySQL database server.

If you want to allow your client to access your MySQL database server, you should give access permission to that IP-Address of the client.

If you want to give permission for 10.0.0.12 ip address, please execute below command.

root# mysql -u root -p
password:

mysql> use mydb;

mysql> GRANT ALL ON *.* to root@'10.0.0.12' IDENTIFIED BY 'root_password'; 

mysql> FLUSH PRIVILEGES;

If you want to allow user from any network, you should perform the below steps.

Change MySQL config file:

/etc/mysql/my.cnf

Comment following lines:

#bind-address           = 127.0.0.1
#skip-networking

If skip-networking line is not present, you can add it and comment it.

Restart MySQL Server:

root #> mysql restart

Login in MySQL and change the grant privileges:

mysql> GRANT ALL ON *.* to root@'%' IDENTIFIED BY 'root_password';

Please also make sure that port 3306 is opend which is default port of MySQL Database Server.

I installed and configured PostgreSQL in one of our client computers and found the problem of TCP/IP.

When a client machine tried to connect the PostgreSQL Server, it got an error like “psql:could not connect to server:Connection refused”.

If you need to the connect all clients with PostgreSQL server, you should perform the below two actions.

Add client IP-Address ranges into pg_hba.conf :
pg_hba.conf is a configuration file which controls the Client Authentication. This file automatically installed when the data directory is initialized.

Below is a default entry in pghba.conf file.

# IPv4 local connections:
host    all         all         127.0.0.1/32          md5
# IPv6 local connections:
host    all         all         ::1/128               md5

In our example, we have a client, IP-Address which is “10.0.0.12”. If you require connecting this client with PostgreSQL Server, please add below entry in the pghba.conf and after that save the file and restart PostgreSQL Service.

host    all         all         10.0.0.12/24    md5

Another method is to change listen_addresses parameter in postgresql.conf :

In the PostgreSQL configuration file (postgresql.conf), by default listen address is “localhost” like,

listen_addresses = 'localhost'

Please change this parameter value from ‘localhost’ to ‘*’ so that all clients can connect from different networks.

listen_addresses = '*'