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

Question

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 rememb

Answer 1

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.

Answer 2

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.

Answer 3

Schemas contains Databases.

Databases are part of a Schema.

So, schemas > databases.

Schemas contains views, stored procedure(s), database(s), trigger(s) etc.

Answer 4

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).

Answer 5

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.

Answer 6

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