Schema

Schema :

• A PostgreSQL database cluster contains one or more named databases.
• A database contains one or more named schemas, which in turn contain tables.
• The same object name can be used in different schemas without conflict;
• A user can access objects in any of the schemas in the database he is connected to, if he has privileges to do so.

Why Schemas :

• 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 cannot collide with the names of other objects.

Creating a Schema :

• To create a schema, use the CREATE SCHEMA command.
• Give the schema a name preferably same as the user name so that it gets associated
  automatically.
• For example: CREATE SCHEMA training;
• Objects in this schema can be referred using schema.table for e.g training.students.
  

Using DDL Statements to Create and Manage Tables

Database Objects :


Naming Rules :

Table names and column names:
– Must begin with a letter
– Must be 1–30 characters long
– Must contain only A–Z, a–z, 0–9, _, and $
– Must not duplicate the name of another object owned by the same user
– Must not be an PostgreSQL server reserved word