SQL Data Types, Commands, Relational Algebra & Calculus
SQL Data Types and Their Purpose
SQL data types specify the type of data that can be stored in a database table. Choosing the correct data type improves storage efficiency, performance, and data integrity.
Numeric Data Types
These types are used to store numeric values.
- INT / INTEGER – stores whole numbers.
- SMALLINT / BIGINT – stores small or large integers.
- DECIMAL(p, s) / NUMERIC – stores fixed-point (exact) numbers.
- FLOAT / REAL – stores floating-point numbers (approximate).
Character (String)
Read MoreVirtual Memory and Disk Storage Systems
Virtual Memory Fundamentals
Virtual memory provides the separation of user logical memory and physical memory.
- Only part of the program needs to be in memory for execution; therefore, the logical address space is greater than the physical address space.
- It allows address spaces to be shared by multiple processes, which results in less swapping.
- It allows pages to be shared during
fork(), leading to faster process creation.
Page Fault Mechanisms
A page fault occurs the first time there is a reference to
Read MoreJava Exception Handling, Custom Exceptions & File I/O
Java Exception Handling and File I/O
Multiple Catch Statements
In Java, multiple catch statements allow a program to handle different types of exceptions separately. When we write a try block, it may throw different exceptions at runtime. To handle each specific exception, Java provides multiple catch blocks arranged one after another. Multiple catch statements mean writing more than one catch block after a single try block so that each block handles a different type of exception. This helps in writing
Read MoreJava Programming Essentials: OOP and Core Syntax
Java Program Structure
A typical Java application is composed of one or more classes. The most basic structure for a runnable Java program includes:
- Package Declaration (Optional): Specifies the package the class belongs to.
package com.example.app; - Import Statements (Optional): Allows using classes from other packages (like built-in Java libraries).
import java.util.Scanner; - Class Definition: Defines the main structure of the program.
public class MyProgram { // ... Class body ... } - main Method (For Executable
Computer Systems and Digital Documentation Essentials
Understanding Blogs and Weblogs
✍️ Blogs (Weblogs)
A blog (short for “weblog”) is a type of website or a section within a website that features regularly updated content presented in discrete, often informal, diary-style entries called posts.
Key Characteristics of a Blog
- Reverse Chronological Order: Newest posts typically appear first at the top of the page.
- Informal/Conversational Tone: Posts are often written in a personal or conversational style, making them highly engaging.
- Focus on a Topic (
OOP Concepts: Inheritance, Polymorphism, and Exceptions
Definition of Inheritance
Inheritance is an OOP concept that allows a class (called the child or subclass) to acquire the properties and behaviors (fields and methods) of another class (called the parent or superclass).
- It promotes code reusability, modularity, and hierarchical classification.
- The child class can add new features or override existing ones of the parent class.
- Example Structure:
class Parent { /* fields and methods */ }class Child extends Parent { /* additional fields and methods */ }