The document discusses data abstraction concepts in database management, detailing the three levels: physical, logical, and view. It highlights the importance of shielding end-users from unnecessary complexities and explains attributes and properties of relations within a database. Additionally, it touches on domain constraints and provides an example of a SQL command to create a transactions table.

1. Class :XII CS
Total strength: 45
Topic : Data base Concepts
TLO: Data abstraction levels

2. Data abstraction
04/04/2024

3. Introduction
• Video games
• Player plays : not about how scores are stored , what
algorithm or steps or codes are there to run this game.
• How these works on the web.

4. data abstraction entails
shielding end-users from
unnecessary data.
• That means
• hiding unnecessary background details from the end user to
make the accessing of data easy and secure.
• Ex: fridge : end user uses it without bothering about the
microcontrollers inside it
• Algorithms used to work fridge in different mechanism.
Other Examples from students .
Source : Youtube
https://www.youtube.com/watch?v=GEsVo2fsl0g

5. We just place the order-
ecommerce sites
• We book the tickets .
And many more examples are there.

6. Levels of Data Abstraction
in DBMS
• The data abstraction in DBMS is implemented in 3 layers:
• Physical or Internal Level
• Logical or Conceptual Level
• View or External Level

8. Physical : how to store data
• All these racks contain hard disk drives storing all your secured data!
Where the raw data is physically stored as files. This layer
contains all the complex data structures and the data
accessing methods defined.

9. Logical level:
• After taking the raw data from the physical or internal level,
the structure of the data is defined at the logical or
conceptual level
• Designing the database /tables . (Schema/structure)

10. View level:
many users on the same d/b
• He/she does not get the entire database, but depending on
the queries made from the front-end the user gets to see the
data. I

11. Three Important Properties
of a Relation
1. Attribute rules:
• Each attribute in a relation has a unique name.
• Sequence of attributes in a relation is immaterial.
2. Rules on Tuples:
• Each tuple in a relation is distinct.
• Sequence of tuples in a relation is immaterial.
3. Rules on the state of a relation.
• All data values in an attribute must be from the same domain (same
data type).
• Each data value associated with an attribute must be atomic
• No attribute can have many data values in one tuple.
• A special value “NULL” is used to represent values that are unknown or
non-applicable to certain attributes.

12. Properties of dbms

13. Domain:
domain is a set of values that can be stored
in a column of a database table. A domain is
usually defined by a column's data type

14. Introduction to Domain
Domain constraints in DBMS are the set of rules which
defines what kind of attributes can be stored in an entity (a
table that stores data)

15. Foreign Key

16. Sql command
CREATE TABLE TRANSACTIONS(TRANSACTION_ID INT PRIMARY
KEY , AMOUNT FLOAT(6,2) , CUSTOMER_ID INT ,
FOREIGN KEY(CUSTOMER_ID) REFERENCES
CUSTOMERS(CUSTOMER_ID));