SQL Introductions

SQL is the language which is used to interact with database SQL stands for Structure Query Language

Oracle 11G (2007): Oracle is a Database Server which is used to store Data permanently in Secondary Storage Devices.

Data: It is a collection of Row facts

Example: 1. Student Marks       2. Customer Name

Information: Processed Data is called information i.e. when we are processing Data we can achieve Meaningful Results. This is called Information

1 Mark Sheet

2 Invoice of the customer

Data Store: It is a place where we can store Data (or) Information.

1 Books and papers

2 Flat Files

3 Databases.

Flat File: This is Traditional Approach which is used to Store Data (or) Information into the DISK permanently, in this method Data is stored Individual unrelated files, Sometime these files are Also Called as Flat files, In flat file Approach Every Application program maintain its own file separate from another Application program

Disadvantages

1 Data Retrieval

2 Data Redundancy

3 Data Integrity

4 Data Security

5 Data Indexing.

Data Retrieval: To Retrieve Data from flat files then we m used develop application program in high level languages, whereas in Databases we are retrieving Data from the Database using SQL language

Whenever we are installing DBMS software automatically some place is created in Hard Disk, This place is also called as physical database u Also DBMI software automatically creates an creates an user an user interface, Through this user interface we can Directly Interest with the DB (or) through the application program Indirectly Interacting with the database

DATA REDUNDANCY: Sometimes we are maintaining multiple copies of the same Data in different locations this Data is Also called as Redundancy Data In Flat file Mechanism  when we are modifying Date in one locations it is not Effected in Another Location this is Also called as Inconsistency That’s why flat file Does Not Maintain consistent Data Automatically     

Data Model: How Data is layered out at Conceptual level Defined By means of Data Model In the History of DB Design there Data model Have been in use these are

  1. Hierarchical Data model
  2. Network Data model
  3. Relational Data model
  4. Hierarchical Data model

In Hierarchical Data Model Organizes Data I tree like structure this hierarchy is also called parent child hierarchy this Data model is implemented Based one to many Relationship in this Data model also Data is Represented in the format of collection of records in this data model record type is also same as table  in relational data model this data model having more duplicate data because in this data model child segments are always repeated because this data model internally were one to many relationships  and also to retrieve data from this data model developer  must search data based on root note onward their why this data model degrades performance of the Applications hierarchical data model introduced in 1960

Based on this hierarchical data model IBM Introduced IMS product if you want to operate hierarchical data model products then we must use procedural language

NETWORK DATA MODEL: In 1970 CODASYL (conference on data system language committee)Introduced network data model this data model is implemented based on many to many relationship that’s why this data model automatically reduces duplicate data because here child segments are not repeated in this data model also data is represented in the format of  records we also record type is also same as table in relational data model in 1970 IBM introduced IDMS (integrated data management system) Based on network data model to operate this data model product also we are using procedural language

Relational data model: Relational data model was introduced By EF codd in 1970 he wrote a paper relational model of data for large shared data Banks in this paper EF codd introduced relational data model it is a collection of relation (or) collection of two dimensional tables in these two dimensional tables only we can store data or information relational data model consist of three components tree are

  1. Collection of objects
  2. Set of operators
  3. Integrity Rules

All relational data model products operated through SQL language this is a no procedural language