Data model: Data model shows how data is represented in the conceptual level of the database architecture
In the history of database design, 5 database models have been used.
Aptitude
- Introduction
- File System vs DBMS
- Tuple
- Record
- Architecture
- Need of DBMS
- DBMS Abstraciton and Indipendence
- Data Models
- ER Models
- RDBMS
- Relational Data Model
- SQL Introduction
- SQL Types
- DDL Commands
- DQL Commands
- DML Commands
- DCL Commands
- TCL Commands
- Default Constraints
- Check Constraint
- Not Null Constraint
- Unique Constraint
- Key Constraint
- Key In DBMS
- Primary Key
- Foreign Key
- Super Key
- Candidate Key
- Alternate Key
- Composite Key
ER Models
RDBMS
SQL
SQL Constraints
Keys In DBMS
DBMS Data Models
Levels of Data Abstraction
1. Flat File DBMS
- The file management system was the first method used to store data in the computer is a database
- Each data item is stored on a disc sequentially in one large file
- If you want to locate a particular item the search start from the beginning and each item is checked one by one sequentially till the match is found
Drawbacks
Data duplication, very poor security, retrieving of data is very slow, no support for data, types dynamic memory allocation, concurrent data sharing is not allowed, no security mechanism through passwords, etc
2. Relational DBMS
It was first outlined by EF.codd 1970
The 2 components of the relational model are:
- collection of objects or relations that stores the data
- operations that can act on relations to produce other relations
This is the most frequent and commonly database today Data integrity, logical representation in the form of table rows and columns, no data redundancy, logical links between relations are maintained, null, values integrity constraint, provides high security, unlimited size, security, range of data types, multiple users can work at a time
3. Hierarchical DBMS
- organize data like a tree structure, record types are the same as a relational data model
- The hierarchical data model is implemented based on one too many relations between parent and child records
- Because of a parent, child records in one-many relation many child records have single parent records as a result of repetition of child records occur
4. Network DBMS
- in 1970s CODASY(conference on data system language) committee introduced a network data model
- in this data, the model will maintain less duplicate data because their parent-child records are implemented based on many-many relation
- In this model also data is represented in the format of records and also record type is the same as a table in relation format
5. Object-relational DBMS
- In this model relational database but within object-oriented database design
- Object, class, inheritance is directly supported In database schema and the query language
- It provides a middle ground between the relational database and object-oriented database
- are OOPS is added to the relational database design productivity, security boosts a lot
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