different schemas with different tables refer to identical data file - database

We have ONE DB which has TWO schemas as follows:
Do the Names from both Customer tables refer to the same data file location?
If not, is it possible to set them into the same point so in case of changing one the other is changed as well?

In the case of Oracle, you can save both tables in the same datafile depending on your declaration in tablespaces.
If you don't need to duplicate the same data, you can use a synonym, assigning permissions between schemas.

Related

Creating Access Database Copies with different uniqueID

I have multiple access databases with approximately 30 tables each. Each database corresponds to an airplane and its allied tables. Most of the data in these tables is same. Hence, I would just like to change the UniqueID of the first (perfect/tested) database in order to have the same structure for rest of the databases (along with Data) and have multiple databases ready.
I tried the following:
1. Importing data: This creates copies of the data-tables in the new database and then they have to be renamed plus the uniqueID problem persists.
Broke all relationships of the main table, changed the Primary Key and again proceeded to add relationships. This is somehow not a good solution as it complicates the work.
Copied data by modifying tables in Excel and then pasting data in Access. In this I kept a lookout for the IDs in each table and modified accordingly. This is also a tedious process.
I am looking for a good solution and suggestions. Thanks in advance!

DB2 table full name

I'm getting a little confused in db2 table naming. In db2 we have tablespace, schema, database name, username, table name, etc... .
My (silly) question is: When querying (i.e. select * from ???), what is the full and complete name of a table? As in some situations it doesn't work if I put just the table name. (i.e. tablespace and schema are also required.)
For example, in MySQL it is [database].[table]. But what about DB2?
Thanks a lot for your attention.
In DB2 you connect to a database and then select from a schema and table name
schema.tablename
For an end user that is it. In the background there can be crazy stuff going on with nicknames -- any surfaced schema.tablename can be an alias to anywhere else (even other servers with federation), but from the query point of view it is in that schema.tablename location.
tablespaces and indexspaces are used internally to map where the data is stored on the disk and only matters when you are creating the table.
bufferpools are used internally to map where the data is stored in memory and only matter when you create tablespaces.
Other objects (Views, Indexes, Stored Procedures, Functions, and Sequences) are just like tables
schema.<objectname>
Special Characters
In DB2 you can have special characters in names. You use " to around the special names
schema."tablename with space"
Quotes are also needed if you combine upper and lower case in your names. DB2 will convert to upper case if the name is declared in upper case so a leading practice is to use upper case and underscore in all names -- then you don't need to worry about quoting or matching case.

Linking table in same SQL Server database to find or match data easier

I will be having multiple tables depends on how many type of data I will be receive after reading a file.
So far I have done creating and insert all the data accordingly into multiple tables where they should belong to.
How to link those table together in a same database so that I can find the repeated data in different tables.
I need to match all the multiple tables together so that I can find or match all the data together to see how many times they have appear in different tables and allocate where are them. Is there anyway to do so? My previews coding is done in Python Pyodbc module, about this linking table, it can be done in a SQL Server query right?
When I want to know how many times the 4 has appear in the column No_Person_in_the_room in both tables or more tables, it will shows the number of 4 has appear how many times in all the tables
And also
1) Honestly there should be just one table (PersonRoleRelationship) which will hold all relationships between different Person roles (because same person can have different roles in different relationships). This structure would make it very simple to query the Parent - Child relationship to query. A sample database structure will look like this:
2) If the database redesign is not possible, then you can add a new column having calculated hash values for the columns you need which can then be used to compare among different tables.

cakephp - saving data of two tables in different databases

I have 2 tables in different databases. I joined the information in the same dropdownlist. But when i try to save data, the system does not know which table to get the selected id. it is just checking one of the tables.
is important to note that the ids (of two tables) are different.
its possible to do this?
thanks

What is the difference between a schema and a table and a database?

This is probably a n00blike (or worse) question. But I've always viewed a schema as a table definition in a database. This is wrong or not entirely correct. I don't remember much from my database courses.
schema -> floor plan
database -> house
table -> room
A relation schema is the logical definition of a table - it defines what the name of the table is, and what the name and type of each column is. It's like a plan or a blueprint. A database schema is the collection of relation schemas for a whole database.
A table is a structure with a bunch of rows (aka "tuples"), each of which has the attributes defined by the schema. Tables might also have indexes on them to aid in looking up values on certain columns.
A database is, formally, any collection of data. In this context, the database would be a collection of tables. A DBMS (Database Management System) is the software (like MySQL, SQL Server, Oracle, etc) that manages and runs a database.
In a nutshell, a schema is the definition for the entire database, so it includes tables, views, stored procedures, indexes, primary and foreign keys, etc.
This particular posting has been shown to relate to Oracle only and the definition of Schema changes when in the context of another DB.
Probably the kinda thing to just google up but FYI terms do seem to vary in their definitions which is the most annoying thing :)
In Oracle a database is a database. In your head think of this as the data files and the redo logs and the actual physical presence on the disk of the database itself (i.e. not the instance)
A Schema is effectively a user. More specifically it's a set of tables/procs/indexes etc owned by a user. Another user has a different schema (tables he/she owns) however user can also see any schemas they have select priviliedges on. So a database can consist of hundreds of schemas, and each schema hundreds of tables. You can have tables with the same name in different schemas, which are in the same database.
A Table is a table, a set of rows and columns containing data and is contained in schemas.
Definitions may be different in SQL Server for instance. I'm not aware of this.
Schema behaves seem like a parent object as seen in OOP world. so it's not a database itself. maybe this link is useful.
But, In MySQL, the two are equivalent. The keyword DATABASE or DATABASES
can be replaced with SCHEMA or SCHEMAS wherever it appears. Examples:
CREATE DATABASE <=> CREATE SCHEMA
SHOW DATABASES <=> SHOW SCHEMAS
Documentation of MySQL
SCHEMA & DATABASE terms are something DBMS dependent.
A Table is a set of data elements (values) that is organized using a model of vertical columns (which are identified by their name) and horizontal rows. A database contains one or more(usually) Tables . And you store your data in these tables. The tables may be related with one another(See here).
As per https://www.informit.com/articles/article.aspx?p=30669
The names of all objects must be unique within some scope. Every
database must have a unique name; the name of a schema must be unique
within the scope of a single database, the name of a table must be
unique within the scope of a single schema, and column names must be
unique within a table. The name of an index must be unique within a
database.
From the PostgreSQL documentation:
A database contains one or more named schemas, which in turn contain tables. Schemas also contain other kinds of named objects, including data types, functions, and operators. The same object name can be used in different schemas without conflict; for example, both schema1 and myschema can contain tables named mytable. Unlike databases, schemas are not rigidly separated: a user can access objects in any of the schemas in the database he is connected to, if he has privileges to do so.
There are several reasons why one might want to use schemas:
To allow many users to use one database without interfering with each other.
To organize database objects into logical groups to make them more manageable.
Third-party applications can be put into separate schemas so they do not collide with the names of other objects.
Schemas are analogous to directories at the operating system level, except that schemas cannot be nested.
Contrary to some of the above answers, here is my understanding based on experience with each of them:
MySQL: database/schema :: table
SQL Server: database :: (schema/namespace ::) table
Oracle: database/schema/user :: (tablespace ::) table
Please correct me on whether tablespace is optional or not with Oracle, it's been a long time since I remember using them.
As MusiGenesis put so nicely, in most databases:
schema : database : table :: floor plan : house : room
But, in Oracle it may be easier to think of:
schema : database : table :: owner : house : room
More on schemas:
In SQL 2005 a schema is a way to group objects. It is a container you can put objects into. People can own this object. You can grant rights on the schema.
In 2000 a schema was equivalent to a user. Now it has broken free and is quite useful. You could throw all your user procs in a certain schema and your admin procs in another. Grant EXECUTE to the appropriate user/role and you're through with granting EXECUTE on specific procedures. Nice.
The dot notation would go like this:
Server.Database.Schema.Object
or
myserver01.Adventureworks.Accounting.Beans
A Schema is a collection of database objects which includes logical structures too.
It has the name of the user who owns it.
A database can have any number of Schema's.
One table from a database can appear in two different schemas of same name.
A user can view any schema for which they have been assigned select privilege.
I try answering based on my understanding of the following analogy:
A database is like the house
In the house there are several types of rooms. Assuming that you're living in a really big house. You really don't want your living rooms, bedrooms, bathrooms, mezzanines, treehouses, etc. to look the same. They each need a blueprint to tell how to build/use them. In other words, they each need a schema to tell how to build/use a bathroom, for example.
Of course, you may have several bedrooms, each looks slightly different. You and your wife/husband's bedroom is slightly different from your kids' bedroom. Each bedroom is analogous to a table in your database.
A DBMS is like a butler in the house. He manages literally everything.
In oracle Schema is one user under one database,For example scott is one schema in database orcl.
In one database we may have many schema's like scott
Schemas contains Databases.
Databases are part of a Schema.
So, schemas > databases.
Schemas contains views, stored procedure(s), database(s), trigger(s) etc.
A schema is not a plan for the entire database. It is a plan/container for a subset of objects (ex.tables) inside a a database. This goes to say that you can have multiple objects(ex. tables) inside one database which don't neccessarily fall under the same functional category. So you can group them under various schemas and give them different user access permissions. That said, I am unsure whether you can have one table under multiple schemas. The Management Studio UI gives a dropdown to assign a schema to a table, and hence making it possible to choose only one schema. I guess if you do it with TSQL, it might create 2 (or multiple) different objects with different object Ids.
A database schema is a way to logically group objects such as tables, views, stored procedures etc. Think of a schema as a container of objects.
And tables are collections of rows and columns.
combination of all tables makes a db.

Resources