I need a advice if my idea is good or wrong.
I use opencart and I want to create 2 store. Let's say I have this:
site1 use db1
site2 use db2
What I want is for table from db1 like address,customer,orders also to be use it on db2 by site 2.
Is any way to share a table from db1 to db2? and also let site2 to modify,edit,select from this table?!
I know I can use multistore but I don`t want to use this option(many reason). I know also I can modify files from site2 to use db1.address but I believe on My SQL should already have something for what I ask.
I know I can create something like this CREATE VIEW db2.address AS SELECT * FROM db1.address but I understand this is not the best idea because have some limitation.
There is no use in creating same tables in different schemas, because updates and deletes would be an overhead then.
Either you can go with creating a schema named GLOBAL
which will the physical existence of the table and the rest schema will use its view
OR
You can create a VIEW of the table in other schemas.
Related
I have access to a remote database, and I would like to dump the schema and data of several views onto my local machine and load this into my local database as tables in a quick and easy way.
I lack the user privileges to run CREATE TABLE AS (SELECT * FROM target_view), otherwise this would be trivial to solve. In other words, I want to retrieve and recreate the "composite" schema of target_view as if it were a table.
I do not want the output of SHOW CREATE VIEW, as this only shows a complex SELECT statement with joins to various tables on remote I have limited ability to access. And a problem I'm seeing in MySQL 8.x is when I run SHOW CREATE TABLE on the view, this command simply acts as an alias of SHOW CREATE VIEW (which is reasonable).
Frustratingly, I can run DESCRIBE and see the schema of these views as they were tables. I really just need to convert this information into a CREATE TABLE statement without actually being able to run CREATE TABLE.
In case it weren't obvious, the key is to avoid manual reconstruction of these views' tabular schemas (as they may change in the future). I also want to avoid the solution of reverse engineering a generic table construction of 20-30 generic VARCHAR or TEXT columns from a CSV dump.
I don't know of any way to display the metadata of a result set in CREATE TABLE syntax.
What I would do given your circumstance is first create on your local MySQL instance the base table and the view, then you can use the CREATE TABLE AS SELECT ... syntax to produce a concrete table to match the metadata of the view result set.
I've been asked to build a module for a web application, which will also be used as a stand alone website. Since this is the case, I wanted to use a separate database, and wondered if there was a way of having a table in one database, be a "pointer" in another database.
For example, I have databases db1 and db2
db1 has table users, so I want to have db2.users point to db1.users.
I know I could setup triggers and what not to sync two seperate tables but this sounds cooler :)
EDIT
So in my code I'm using sql such as
select * from users
Now, at the database level, I want "users" to actually be db1.users. Then, if I want to, I can remove the alias/pointer and "select * from users" will point to the users table in the current database. I guess what I'm looking for is a "global alias" type of thing.
Just use it directly from another database?
SELECT ... FROM `db1`.`users` LEFT JOIN `db2`.`something`
The federated storage engine offers something similar to the feature you asked for.
And if your databases are on the same database server, the federated storage enging sounds a bit like an overkill to me. You may want to create a view instead.
Both methods won't be useful if db1 is not available. As Emmerman already points out, you need to store the data in db2 if you want to prepare for the case of db1 being unavailable.
I got a case where I have several databases running on the same server. There's one database for each client (company1, company2 etc). The structure of each of these databases should be identical with the same tables etc, but the data contained in each db will be different.
What I want to do is keep a master db that will contain no data, but manage the structure of all the other databases, meaning if I add, remove or alter any tables in the master db the changes will also be mirrored out to the other databases.
Example: If a table named Table1 is created in the master DB, the other databases (company1, company2 etc) will also get a table1.
Currently it is done by a script that monitors the database logs for changes made to the master database and running the same queries on each of the other databases. Looked into database replication, but from what I understand this will also bring along the data from the master database, which is not an option in this case.
Can I use some kind of logic against database schemas to do it?
So basicly what I'm asking here is:
How do I make this sync happen in the best possible way? Should I use a script monitoring the logs for changes or some other method?
How do I avoid existing data getting corrupted if a table is altered? (data getting removed if a table is dropped is okay)
Is syncing from a master database considered a good way to do what I wish (having an easy maintainable structure across several datbases)?
How will making updates like this affect the performance of the databases?
Hope my question was clear and that this is not a duplicate of some other thread. If more information and/or a better explantion of my problem is needed, let me know:)
You can get the list of tables for a given schema using:
select TABLE_NAME from information_schema.tables where TABLE_SCHEMA='<master table name>';
Use this list for a script or stored procedure ala:
create database if not exists <name>;
use <name>;
for each ( table_name in list )
create table if not exists <name>.table_name like <master_table>.table_name;
Now that Im thinking about it you might be able to put a trigger on the 'information_schema.tables' db that would call the 'create/maintain' script. Look for inserts and react accordingly.
I have 2 db mysql at two locations, i need to copy the schema from first to the second one without hurting the data that is already existing in the II location.
Is it possible to achieve this?
Please experts help.
Databases are usually too complex to allow a simple "copy".
Use Toad's database comparison/scripting tools (or something like this: http://adamspiers.org/computing/mysqldiff/) to find the differences, check and run them manually.
After dragging two tables in from one database, I switch to another and drag a table in. Now I get a message if I want to replace the connection string with the new one. I want tables from multiple databases in one DBML. Is this possible?
It is entirely possible to reference multiple databases within the same DBML, PROVIDED those databases reside on the same SQL Server.
In Visual Studio, right-click on the DBML, click "Open with..." , and select XML (Text) Editor with Encoding.
You will see your first table that you dragged in looks like this:
<Table Name="dbo.MyTable1fromMyDatabase1" Member="MyTable1fromMyDatabase1">
For your tables from other databases you wish to add, enter them like this:
<Table Name="MyDatabase2.dbo.MyTable1fromMyDatabase2" Member="MyTable1fromMyDatabase2">
This will work assuming the same login works for both databases, and your LINQ expressions can now query across both databases!
I don't believe that what you're looking for is possible, since the DataContext would then not have any easy way of resolving results from two separate databases.
If you're looking to create domain objects from two separate databases, then your best bet would be to have two separate DBML's, then use a bridge (GOF) or some other related design pattern to instantiate your domain objects.
Another option is to create a server link on on database that points to the other and make aliases to the remote tables from the "local" DB. I believe then you'd be able to reference them as if they were all in the same database.
We can also create a view that queries the table in the other database. We can select, insert and update this view, which will affect the table in the other database as well.