I've recently had to do some work on an Oracle database. I come from a MS SQL background. I am still trying to get my head around some basic definitions in Oracle
Schema - to me this just meant the structure of the database. Which includes the structure of the tables, indexes and any constrains. This does NOT include any data that is stored in the tables. A database would only contain one Schema and one set of data.
But in Oracle it seems like a Schema is defined as the structure and the data. And a database can hold many Schemas.
Is that accurate?
Regardless of the database engine, it isn't uncommon to talk about your data model as your "schema". That's not necessarily how any relational database engine defines the term but it may be perfectly clear from the context that you're talking only about the definitions of objects and not the actual data.
In both SQL Server and Oracle, a "schema" is a way of collecting together a bunch of related objects, code, and data. If you define a schema in SQL Server and create a table foo in that schema along with a usp_setFoo procedure, the data that is in foo would be part of that schema. In the same way, an Oracle schema would generally involve table and index definitions, data, code, etc.
Technically, in Oracle, a schema is defined as the set of objects owned by a particular user. Practically, an Oracle schema is generally roughly analogous to a SQL Server "database". Oracle normally has two levels of object naming (schema.object) rather than three levels in SQL Server (database.schema.object). If you're using the enterprise edition of Oracle 12.1 with pluggable databases, that changes things a bit and an Oracle pluggable database can be similar to a SQL Server database.
Related
I have a SQL Server 2016 database with in-memory tables. I'd like to use the database diagram feature to create a graphic to match.
Running SSMS 18.3.1. When I start a new diagram, the in-memory tables are not shown in the drop down. Is there another way to get them on the diagram?
Note: In the official documentation these are called memory-optimized tables. See Introduction to Memory-Optimized Tables
You can't add OLTP object in Database Diagram, not in even in SQL Server 2019.
I thought there should be a way to modify [definition] column in [dbo].[sysdiagrams] but it is HexString of unknown file type. (I tried many formats but its obviously an internal Microsoft type)
Unfortunately, there is no reference to mention that is a not-supported feature. (I send a comment to this page )
OLTP is not supported for database diagram. You do not have access to in-memory tables in the diagram because the diagram does not recognize the essence of a in-memory tables as a table, in fact SQL Server generates a DLL for each created Memory-Optimized Table Type that includes the functions required
for accessing the indexes and retrieving data from the related Memory-Optimized Table Variable
If you run the SQL Profiler tool you'll see there is a column name IsMemoryOptimized in the table data result set that is returned for the memory-optimized table. I think since the Database Diagrams functionality is older (since mssql 2000) and not updated regularly it does not support viewing the newer memory-optimized tables.
more info here:
https://social.msdn.microsoft.com/Forums/sqlserver/en-US/71aa7b6e-c281-4417-8149-2eb6f3830110/sql-server-2016-memory-optimized-tables-not-visible-in-database-diagrams?forum=sqlinmemory
I'm looking for the best (best practice) option for one way replication between two databases. I would like to keep this purely SQL but, can write something in C# or use an ETL tool if there are no other good options.
Current setup:
DB1 - There are three instances of this database. It is a large relational database, the schema is the same for each but, they are separate data pots (no replication). Two databases on a 2012 server and one on a 2014 server
DB2 - There are two instances of this database on seperate servers (Europe, Americas) and the data is merge replicated between the two. The publisher is the 2014 server.
The Goal:
DB2 is tied to some reports. It has one table and a small application attached to that table. Users from many different countries enter data via a small application into DB2 and generate reports out of the application.
DB1 is a relational database that has a very large application on top of it but with fewer users. If users are using the application for DB1 then they should not need to duplicate their records into DB2.
There should be one-way replication from the multiple seperate DB1s into DB2. How quickly this happens is not too important.
The important things are:
No backwards replication occurs from DB2s > DB1s (Data only flows from DB1s into one of the DB2s)
Create, Update, and Delete actions should occur in DB2 based on the results
of a comparisson with DB1 (the one way replication)
Current Approach:
I currently have a flat sql view on each DB1 database that has the same schema as the table in the DB2 db's that the data needs to go into.
The servers are also joined as linked servers.
My though was to do a sort of manually written replication script on one of the DB2 databases that calls the views from the DB1s and does the CUD actions on a timed basis.
It seems to me that there should be an easier way though!?
Any thoughts on how to do this would be very much appreciated.
Keep in mind that since several of the DB1s exist on a SQL 2012 server that there may be some issues as 2012 might not be allowed to be a publisher for replication to a 2014 server.
I read a write up about database schema.
A SQL Server schema is a container of objects. For example you may have a large enterprise application and then is a good practice to use different schemas for different purposes (e.g. put HR related tables into HR schema, accounting related tables into Accounting schema and so on). A schema can be owned by any user, and the ownership is transferable.
They said: use different schemas for different purposes (e.g. put HR related tables into HR schema, accounting related tables into Accounting schema and so on)
Do they mean create new database for HR and again new database for accounting?
Because when we create a database then a single schema is created so we cannot create multiple schema in single SQL Server database as far I know.
So please tell me how is it possible to create different schemas for different purposes in a single database? Thanks
Purpose of Schema
Schemas in sql server were introduced in sql server 2005, The main purpose was to eliminate User's ownership of objects in sql server. or you can say to separate users from objects in sql server.
Prior to Sql server 2005 objects in sql server (Tables, views, Store proceders etc) were owned by users. Typically the user who created it.
And that user had to give permissions to other users to use that particular object.
Imagine a scenario where 12 developers are working in a company and all developers are creating sql objects left, right centre. Now all the developers had to give permissions to other 11 developers if they had to work objects created by that one developer. quite a bit of mess isnt it??
Since sql server 2005 came with Schema. All the objects were Owned by a Schema Not a User. if you havent created any custom schema it will be under default Schema dbo.
Now anyone who has permission to dbo schema has permission to any object under dbo schema.
Why it is a good idea to create different schemas for different departments in your case. It may be because HR people doesnt need to know anything about Finance stuff. so you can create a HR schema and give HR people permission only on HR schema. and vice versa with finance people. That will restrict their access to only objects related to their departments.
And we can create multiple Schemas in one database if you have ever worked with Adventureworks database, it has Schemas like 'Production', 'Sales' etc etc.
Read here to learn more about schemas in sql server.
No they mean create a schema. Create schema works within a database. There are all sorts of uses for it, I tend to think of it as either namespacing or a more natural way of partitioning a smallish database and keeping role based access, where you can think of schema as a user group.
Unfortunately, there are two meanings to the word "schema" in the database world.
One means the overall design of the database tables. "Show me your database schema", for example. This would be the collection of "create table" commands, or and ERD diagram.
The other is a synonym for "namespace", which the article in question is referring to. You can store tables, functions etc in different namespaces to ease cognitive load or use for security grouping.
we are working on data migration of sql server 2000 to Oracle 11g. Sql server has 4 databases which has to be migrated. These 4 databases are used for 6 different standalone applications. Oracle is installed in Unix server. Can we create a single database and different schemas for each sql server database or do I need to create multiple databases or can I use single database, single schema and multiple tablespaces or any other procedure to maintain the performance?
You can create multiple Oracle databases. Or you can create a single database with multiple schemas. Or you can create a single database with a single schema an put everything there if all your object names are unique.
The most similar approach would generally be to create a single Oracle database with four schemas. That gives you four separate namespaces in case you have objects in two different SQL Server databases that have the same name. And a single Oracle database per server generally gives the best performance since you're not allocating multiple SGAs and PGAs in memory or running multiple sets of background processes.
Tablespaces in Oracle are a completely separate concept. They have nothing to do with namespaces or permissions. They simply allow you to determine which objects reside in which physical data files. Barring something extremely unusual, tablespaces have nothing to do with performance. You could have the objects in all four schemas use a single tablespace. Or you could create four separate tablespaces. Or you could create multiple tablespaces that each have objects from different schemas. My guess is that the simplest approach is to create one tablespace per schema so that you can manage each application's disk space allocation separately.
Ive run into the issue where I need to query 2 separate databases(same instance) in one query.
I am used to doing this with mysql, but Im not sure how to do it with DB2.
In mySQL it would be something like:
SELECT user_info.*, game.*
FROM user_info, second_db.game_stats as game
WHERE user_info.uid = game.uid
So the question is how i translate a query like that into DB2 syntax?
Equivalent of this
Is there a reason why you have the tables in a separate database? MySQL doesn't support the concept of schemas, because in MySQL a "schema" is the same thing as a "database". In DB2, a schema is simply a collection of named objects that lets you group them together.
In DB2, a single database is much closer to an entire MySQL server, as each DB2 database can have multiple schemas. With multiple schemas inside the same database, your query can run more or less unchanged from how it is written.
However, if you really have 2 separate DB2 databases (and, for some reason, don't want to migrate to a single database with multiple schemas): You can do this by defining a nickname in your first database.
This requires a somewhat convoluted process of defining a wrapper (CREATE WRAPPER), a server (CREATE SERVER), user mapping(s) (CREATE USER MAPPING) and finally the nickname (CREATE NICKNAME). It is generally easiest to do these tasks using the Control Center GUI because it will walk you through the process of defining each of these.