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I'm really confused with the terms database, user and schema. Can anyone explain how they are different from each other (if they are)?

If they are same then, what are the similarities between them? How do we use them? And how do we create them?

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5 Answers 5

up vote 24 down vote accepted

In Oracle, users and schemas are essentially the same thing. You can consider that a user is the account you use to connect to a database, and a schema is the set of objects (tables, views, etc.) that belong to that account.

See this post on Stack Overflow: difference between a User and a Schema in Oracle? for more details and extra links.

You create users with the create user statement. This also "creates" the schema (initially empty) - you cannot create a schema as such, it is tied to the user. Once the user is created, an administrator can grant privileges to the user, which will enable it to create tables, execute select queries, insert, and everything else.

The database is the thing that contains all the users you've created, and their data (and a bunch of predefined system users, tables, views, etc. that make the whole thing work). You should look at the Oracle Database Architecture documentation in the Concepts Guide (actually, that whole page is worth a read - there's a section about users and schemas higher up in that page) to get an introduction to what a database is, and what a database instance is - two important concepts.

You can create a database with the create database statement, once you've installed the Oracle software stack. But using dbca (database creation assistant) is easier to get started.

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According to the way the terminology is sometimes used, a USER and a SCHEMA are somewhat similar. But there is also a major difference. A USER can be called a SCHEMA if the "USER" owns any object, otherwise it will only remain a "USER". Once the USER owns at least one object then by virtue of all of your definitions above... the USER can now be called a SCHEMA.

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I am telling you according to concepts not based on any type of database management system you are using.

Conceptually: Database : is Just a pile of data, mostly un-managed related or unrelated data.

Schema: Schema refers to formally structuring the unmanaged related/unrelated data so that it can be managed by some management system which understands the formal definition provided by the schema. Schema is basically a scheme to to provide overview. For example you have XSD which defines the schema to create XML. You have RDBMS which defines its own schemas which are based on Codd Rules which basically defines schemes to create RDBMS.

Now if you want to know more about is refer this Link.

User's use the formal language specified by the schema to access the Database

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I would add that the statements above apply to Oracle's implementation but other databases including SQL Server and PostgreSQL use schema as just a namespace, i.e. a way to group objects. For example, the Staging schema could group all object used in staging data, the Accounting schema could group all objects related to Accounting.

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Not sure to what you refer when you say "statements above" but schema in SQL and in Oracle is a permissions grouping. In other words it is not just a way to group like objects together, but a way to group objects which will ease the management of permissions as you can grant permissions to a schema and therefore avoid having to grant permissions to each object within the schema. – Thronk Nov 23 at 2:29

User!= Schema , User and Schema are not same but they are used interchangeably

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Please add details regarding how they're different. – Erik Sep 10 at 14:55

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