I would like to have a new table with FEDERATED engine, created (cloned) from another existing InnoDB table. Something like this:
CREATE TABLE balance_live
AS SELECT * FROM balance
ENGINE=FEDERATED
CONNECTION='mysql://user:pass#8.8.8.8:3306/db/balance'
But this doesn't work for some reason.
You need an actual table definition, specified explicitly. It's not a view, it's a table. See here for the correct syntax:
https://dev.mysql.com/doc/refman/8.0/en/federated-create-connection.html
Do SHOW CREATE TABLE balance; on the remote host and use that as the definition, just change ENGINE=FEDERATED and add the CONNECTION clause.
As mysql manual on creating federated tables says:
Create the table on the local server with an identical table definition, but adding the connection information that links the local table to the remote table.
You cannot use the as select ... , since in the from clause you can only specify a local table. It is the federated table that creates the link to the remote table.
Just copy the table definition over from the remote table.
Related
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)?
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.
In MySQL, using MySQL Workbench, how can you create a foreign key relationship to a table which resides in another database? After entering the 'Qualified Table Name', of DatabaseName.TableName.ColumnName, workbench simply acts like I put nothing in the box. Do I need to create these relationships only with manual query in workbench if it is a different database?
InnoDB engine allows you to define FK(Foreign Key) for tables.(even from other databases)
For this you must mention database name before table and column name. Like so :
dbname.tablename.columnname
I think I found the solution. Actually you have to add another schema in your Model which represents your 'different' database.
Then you need to create all your tables (in an EER Diagram) into this new Schema.
Finally, when you'll click on the Foreign Keys tab from the original table you'll be able to choose the right table from the different database in Referenced Table. For example different.new_table
I think it is impossible to do what you want. You can not link tables from different databases.
I'm trying to create some meta-data to extend mysql functionality but I can't create tables in the database INFORMATION_SCHEMA. I thought that I could just create another database and have my metadata in there but I need some foreign keys from my tables to some tables in the INFORMATION_SCHEMA DB. Nevertheless, I get errors when trying to create them. Then I thought I could create a trigger to get notified of changes but since triggers are associated to a table and I can't alter that database, I can't create triggers either.
Specifically I have some tables that references to information_schema.schemata(schema_name) and to information_schema.schemata(columns) and some others. I want to have those foreign key so I can use ON UPDATE CASCADE ON DELETE CASCADE or otherwise I'll have some rows in my tables referencing to nothing and I can't allow that.
I'm using mariaDB 5.5.30 which uses MySql 5.3.
INFORMATION_SCHEMA tables are actually views whose contents is automatically maintained by the MySQL server.
The manual gives more information:
Inside INFORMATION_SCHEMA there are several read-only tables. They
are actually views, not base tables, so there are no files associated
with them, and you cannot set triggers on them. Also, there is no
database directory with that name.
Although you can select INFORMATION_SCHEMA as the default database
with a USE statement, you can only read the contents of tables, not
perform INSERT, UPDATE, or DELETE operations on them.
They are not really views but temporary tables, that's why you don't see folders.
show create view views;
ERROR 1347 (HY000): 'information_schema./tmp/#sql_2ac_0' is not VIEW
My project has its own database. Also, I use table of users, which is on other database. Two offices have their data on the same server, but third one has its own user table on other server.
So, in lots of queries I need to join either table some_db.users or other_server.some_db.users
What solution would you advise for this scenario?
I use MySQL.
There is Federated tables in MySQL:
The FEDERATED storage engine lets you access data from a remote MySQL
database without using replication or cluster technology. Querying a
local FEDERATED table automatically pulls the data from the remote
(federated) tables. No data is stored on the local tables.
First, you must have a table on the remote server that you want to access by using a FEDERATED table. Suppose that the remote table is in the sakila database and is defined like this:
CREATE TABLE test_table (
id INT(20) NOT NULL AUTO_INCREMENT,
name VARCHAR(32) NOT NULL
PRIMARY KEY (id)
)
ENGINE=MyISAM
DEFAULT CHARSET=latin1;
Next, create a FEDERATED table on the local server for accessing the remote table:
CREATE TABLE federated_table (
id INT(20) NOT NULL AUTO_INCREMENT,
name VARCHAR(32) NOT NULL
PRIMARY KEY (id)
)
ENGINE=FEDERATED
DEFAULT CHARSET=latin1
CONNECTION='mysql://fed_user:fed_user#197.186.1.199:3306/sakila/test_table';
Sample connection strings:
CONNECTION='mysql://username:password#hostname:port/database/tablename'
CONNECTION='mysql://username#hostname/database/tablename'
CONNECTION='mysql://username:password#hostname/database/tablename'
The basic structure of this table should match that of the remote table, except that the ENGINE table option should be FEDERATED.
Execute:
show variables like '%federated%';
to check if FEDERATED storage engine is available on your local server.
The table federated_table in localhost becomes virtual table of test_table in remote server.
Now you can use the JOIN between the tables in a DB in the localhost server. If there is a table called test in your localhost server, and you want to JOIN with the former sakila.test_table which is in the remote server, write a query like the one shown below:
SELECT * FROM `federated_table` JOIN `test`;
The federated_table in the query will actually refer to test_table in remote server.
On enabling FEDERATED Storage Engine
The FEDERATED storage engine is not enabled by default in the running server; to enable FEDERATED, you must start the MySQL server binary using the --federated option.
NOTE:
Optional storage engines require privileges and will fail to load when --skip-grant-tables is specified.
The result the entire db will fail to load and the following error will appear in the logs:
110318 21:37:23 [ERROR] /usr/local/libexec/mysqld: unknown option '--federated'
This in turn means that an upgrade from 5.x needs to be done in two steps if you have federated tables. Once with --skip-grant-tables and without --federated, the once without --skip-grant-tables and with --federated.
Source: The FEDERATED Storage Engine
Please mention the databse also.
In SQLServer you can use Linked sever. http://msdn.microsoft.com/en-us/library/ms188279.aspx
In MySQL, you can join tables from different databases using fully qualified names like
`database_name1`. `table_name1` JOIN `database_name2`.`table_name2`
But i fear, you cant join tables from different servers because for that you need to have two different connections and as per my knowledge there are no fully qualified connection names to be used in the query.
Alternatively, you can create local temporary table(s) on one of the servers and run the query there on. But in this case you will need to transfer data from one server to another. You can use MySQL GUI tool like SQLyog or MySQL admin, to transfer data from one server to another and to synchronize databases on two servers.
Hope it helps....
Federated tables are your solution for tables on other servers. They are very slow though if you perform joins on them.
If you just want to read data from another database on the same server you can use a view. This way you have all tables virtually in one database and you have to open only one connection in your application.
CREATE
VIEW `my_db`.`table_name`
AS
(SELECT * FROM `other_db`.`table_name`);
MS SQL Server has a TABLE data type which can be used in stored procedures,
Does anybody know if MySQL has an equivalent data type?
I've had a look over the docs but can't seem to find anything, so I presume it doesn't exist, but perhaps somebody has created a workaround
Neil,
MySQL has no such data type and I believe it is good that it doesn't. To achieve similar results, use CREATE TEMPORARY TABLE construction. Name clashes are avoided by having per connection temporary tables:
A TEMPORARY table is visible only to the current connection, and is dropped automatically when the connection is closed. This means that two different connections can use the same temporary table name without conflicting with each other or with an existing non-TEMPORARY table of the same name. (The existing table is hidden until the temporary table is dropped.)
Hope it helps.