• A schema can organize a database.process flow image by Christopher Hall from Fotolia.com
  
  There are different kinds of databases. One is a flat file database, which similar to a spreadsheet with rows and columns. A phone book is a flat file database. Another kind of database is a relational database. This has a structure of smaller, interrelated parts called tables. Common elements join the tables together. For example, a medical database can have a patient table, an insurance table and a diagnosis table. However, a common schema, such as the patient and medical condition, ties them together.
  
  

Database Schema

• Schemas are the organizing principle in a database. The schema does not tell the developer what data to put into the database, but rather what type of data it must contain. Schema themselves may or may not exist in a database; there is an abstract level to them. In general, a schema occurs at the higher levels of abstraction, above programming. They are design models recorded in documents and created by business analysts and database designers.
  
  For example, a database administrator (DBA) might organize a manufacturing database to include product name, product cost, manufacturing time, supplier and labor costs. However, the organizing schema might be to create a television set. The schema specifies the type of data that is entered into the system.
  
  

Relational Database Schema

• A relational database schema specifies a collection of tables. This provides a working structure for the data housed in the database instance.
  
  The purpose of the manufacturing database in the above example is to build a television set. However, in a relational database, each of the tables has an organizational element that relates one table to the other so that a complete television product data description exists through the use of all of the tables.
  
  Each table references another table like a chain by having a common element between the tables. In this way, the schema--which is to build a television set--exists within the database, with the common tables making the connection. The schema does not exist through one table, but from all of them together acting to describe the data for building a television set.
  
  

Oracle Database Schema

• To see the schema types in operation, we can look at an Oracle database schema. Oracle is a company that designs database software to develop applications. In Oracle databases, a schema exists as a schema object. This is part of the structure of an Oracle database. Here, schema objects can represent a developer's conceptual model of the knowledge captured in an enterprise database. The DBA may be responsible for the enterprise database, but now the programmer can have a say in the way the schema interacts with the data. In this way, there can be many schemas associated with one physical database.