What is the connection in mysql? - mysql

Question

I'm trying to do a query like this:
CREATE TABLE Connection_Properties (
COL VARCHAR(30) NULL
)
CONNECTION = 'mysql://localhost:3306/DOCKER2'
PASSWORD = '1234';
Although the schema called docker2 entered in connection does not exist, it is shown that the above query has been performed.
What is the role of that keyword, and if that is done, how to retrieve connection information and password information from that table (Connection_Properties)?

Answer 1

An example of creating and accessing the table with FEDERATED engine.
Enabling FEDERATED Engine.
Stop the server.
Open my.ini and add federated line to [mysqld] section.
Start server and ensure that it is started normally.
Execute show engines; and ensure that FEDERATED storage engine support is enabled.
Creating and accessing FEDERATED table.
Create a table and insert some data in it. The table will be created using default engine (InnoDB in my case).
USE test
CREATE TABLE local_test (id INT, val INT);
INSERT INTO local_test VALUES (1,11), (2,22);
Create FEDERATED table connected to the above table.
CREATE TABLE federated_test (id INT, val INT)
ENGINE=FEDERATED
CONNECTION='mysql://username:password#localhost:3306/test/local_test';
Pay attention - only table structure with specified connection properties is created, the connection is not established and is not even checked!
Work with FEDERATED table.
SELECT * FROM federated_test; -- 2 rows are selected
INSERT INTO federated_test VALUES (3,33); -- insert 3rd row
SELECT * FROM local_test; -- and check that it was inserted successfully
Drop FEDERATED table.
DROP TABLE federated_test; -- drop FEDERATED table definition
SELECT * FROM local_test; -- ensure that this is not effected the local table
local_test is accessed directly.
federated_test is accessed remotely. When the query which needs to access this table is executed then local server establishes a connection to remote server according the connection options (protocol, address and port of the remote server, username and password for to authenticate), accesses specified remote table in specified remote database, receives the answer and uses it in the query. In the query text there is no difference does the table is local or remote.