1. THE THREE LEVEL ARCHITECTURE OF DBMS A.EXTERNAL LEVEL OR SUBSCHEMA B.CONCEPTUAL LEVEL OR CONCEPTUAL SCHEMA C.INTERNAL LEVEL OR PHYSICAL SCHEMA A.EXTERNAL LEVEL OR SUBSCHEMA B.CONCEPTUAL LEVEL OR CONCEPTUAL SCHEMA C.INTERNAL LEVEL OR PHYSICAL SCHEMA

2. EXTERNAL LEVEL OR SUBSCHEMA It is the highest level of database abstraction where only those portions of the database are included which are of concern to user or application program. It consists of the definition of the logical records and relationships in the external view. It also contains the method of deriving the objects in the external view from the objects in the conceptual view. The objects include entities, attributes and relationships. It is the highest level of database abstraction where only those portions of the database are included which are of concern to user or application program. It consists of the definition of the logical records and relationships in the external view. It also contains the method of deriving the objects in the external view from the objects in the conceptual view. The objects include entities, attributes and relationships.

3. CONCEPTUAL LEVEL OR CONCEPTUAL SCHEMA One conceptual view represents the entire database. The conceptual schema defines this conceptual view. It describes all the records and relationships included in the conceptual view. This schema contains the method of deriving the objects in the conceptual view from the objects in the internal view

4. INTERNAL LEVEL OR PHYSICAL SCHEMA It indicates how the data will be stored and describes the data structures and access methods used by the data base. It contains the definition of the stored record, the method of representing the data fields,expresses the internal view and the access aids used.

5. TYPES OF DATABASES 1.OPERATIONAL DATABASES 2.DISTRIBUTED DATABASES 3.EXTERNAL DATABASES 4.HYPERMEDIA DATABASES

6. OPERATINAL DATABASES : operational databases store detailed data needed to support the business processes and operations of a company. They are also called subject area database and production database. EXTERNAL DATABASES : access to a wealth of information from external databases is available for a fee from commercial online services. Websites provide an endless variety of hyperlinked pages of multimedia documents in hypermedia database for you to access

7. DISTRIBUTED DATABASES : many organizations replicate and distribute copies or parts of databases to network servers at a variety of sites. Distributed databases may be copies of operational or analytical databases, hypermedia or discussion databases. Replication and distribution of databases are done to improve database performance at end user worksites. HYPERMEDIA DATABASES : a websites stores such information in a hypermedia database consisting of hyperlinked pages of multimedia( text, graphic, images, vedio clips and so on).the set of interconnected multimedia pages at a website is a database of interrelated hypermedia page elements, rather than interrelated data records. DISTRIBUTED DATABASES : many organizations replicate and distribute copies or parts of databases to network servers at a variety of sites. Distributed databases may be copies of operational or analytical databases, hypermedia or discussion databases. Replication and distribution of databases are done to improve database performance at end user worksites. HYPERMEDIA DATABASES : a websites stores such information in a hypermedia database consisting of hyperlinked pages of multimedia( text, graphic, images, vedio clips and so on).the set of interconnected multimedia pages at a website is a database of interrelated hypermedia page elements, rather than interrelated data records.

8. TYPES OF DATABASE STRUCTURES HIERARCHICAL MODEL NETWORK MODEL RELATIONAL MODEL

9. HIERARCHICAL MODEL A C B E F D GHI

10. NETWORK MODEL network related data sets are similar to hierarchical ones, except that a node may have more than one parent. Hierarchical DBMS is a subset of network DBMS M NP QRS T EFG H JI

11. RELATIONAL MODEL Product number typecolorQuantity in stock Supplier number 2589tablewhite426 2892chairblue630 3471chairLight green 20133 3678deskbrown9150 3689stoolbrown25159 In this model we have the same concept of files, records, and fields. Files are represented by two dimensional tables, each of which is called a “relation.” Records which are viewed as rows in table are called “tuples”. Fields are viewed as columns and are called by attribute names or domain Supplier numberSupplier nameAmount of purchase 30PANKAJ26,035.00 26DINESH13,960.00 159RAJESH75,286.00

12. Basic operations of relational DBMS 1.Create or delete rows 2.Update, insert, or delete rows 3.Add or delete columns 4.Copy data from one table to another 5.Print, recognize or read a table or row