Computer Science Class - 12 Notes
Python
Python is a high-level, interpreted programming language known for its simple, readable syntax and broad versatility. It supports multiple programming paradigms, including procedural, object-oriented, and functional programming. Python is widely used in web development, data analysis, artificial intelligence, automation, and software development due to its large standard library and a vast ecosystem of third-party packages.
Keywords & Identifiers
Keywords are reserved words. Each keyword has a specific meaning to the python interpreter, and we can use a keyword in our program only for the purpose for which it has been defined.
Identifier : In programing languages, identifiers are names used to identify a variable, function or other entities in a program.
Common Keywords : True, def, and, del.
Variables
Container for storing data. It allocates memory to store data values.
Operators in Python
- Arithmetic Operator
- Comparison Operator
- Logical Operator
- Assigment Operator
- Identity Operator
- Membership Operator
Flow Control
- Selection - Conditional ( if, elif, else )
- Repetition - loops ( for, while )
for loops are used to traverse through a sequence.
Data Structures
String
Sequence of characters.
Created using a single quote, double quote, triple quotes.
Characters in string can be accessed using indexes.
String Operations
- Concatenation
- Repetition
- Membership
- Slicing
String Functions
- len
- title
- count
- split
- partition
List
- sequence data type
- store multiple values
- can store different data types.
Tuple
- sequence data type
- store multiple values
- can store different data types.
- Tuple is immutable
Dictionary
- Items are stored as key value pairs.
- keys are unique.
Functions
Code block that is executed on call. Functions can take in positional and keyword arguments.
Database Management
Limitation of File System ( Need or Database )
- DATA COMPLEXITY
- DATA REDUNDANCY
- DATA INCONSISTENCY
- DATA ISOLATION
- DATA DEPENDENCY
- UNCONTROLLED DATA SHARING
Characteristics of Database Management Sytem
- IT HIDES CERTAIN DETAILS ABOUT HOW DATA ARE ACTUALLY STORED AND MANAGED.
- IT PROVIDES USERS WITH AN ABSTRACT VIEW OF DATA.
- IT PROVIDES SET OF PROGRAMS TO MANAGE STORED DATA.
- IT ACTS AS AN INTERFACE BETWEEN DATABASE AND END USER APPLICATION PROGRAMS.
- IT CAN BE OF ANY SIZE AND COMPLEXITY.
Uses
- BANKING
- INVENTORY
- PAYROLL
- ONLINE SHOPPING
- RESERVATION SYSTEM
- HEALTHCARE
RDBMS
RDBMS stands for : Relational Database Management System.
Relation : Table
Attribute - Column
Tuple - Row
Domain - Data Type
Degree - Number of Columns
Cardinality - Number of Rows
Keys - Validations ( Primary Key )
If a table has 4 Rows, its cardinality is 4.
If a table has 4 Column, its degree is 4.
Primary Key
Primary key ensures uniqueness of a row / tuple.
primary key ensures field is not left NULL.
A table can have max 1 primary key.
Foreign Key
A primary key of another table, it is used to connect a row from a table to another table. It ensures relationship between tables.
A table can have more than one foreign key in a table.
Candidate Key
ATTRIBUTES WHICH ARE CANDIDATE FOR PRIMARY KEY
Alternate Key
CANDIDATE KEY LEFT AFTER CREATING PRIMARY KEY.
Data Definition Language ( DDL )
DDL is used to define structure and constraints of data.
It also defines key constraints, relationships between tables, and other data validation constraints.
Examples:
CREATE DATABASE - Create a new Database
CREATE TABLE - create a new table.
ALTER TABLE - modifies a table.
DROP TABLE - deletes a table.
Data Manipulation Language - DML
Used to insert, modify and delete in a database.
SELECT - EXTARCT DATA FROM A TABLE.
UPDATE - UPDATES DATA IN A TABLE.
DELETE - DELETES DATA FROM A TABLE.
INSERT INTO - INSERTS NEW DATA INTO A TABLE.
MYSQL
Common Data Types :
-
CHAR
-
VARCHAR
-
DATE
-
INTEGER
-
DECIMAL