All about DBMS- basics, transaction, acid properties, security..

1. Database Management System (DBMS) A DBMS is a software system designed to create, manage, and retrieve data efficiently while providing an interface between users and the underlying database. It ensures data integrity, security, and consistency by managing concurrent access and reducing data redundancy. Common examples include relational systems like MySQL and PostgreSQL, which organize data into tables, as well as NoSQL systems like MongoDB for unstructured data. 2. SQL Injection (SQLi) SQL Injection is a critical web security vulnerability that occurs when an attacker inserts malicious SQL code into input fields (like login forms) to manipulate back-end database queries. If successful, it allows unauthorized parties to view sensitive data, modify or delete records, and in some cases, gain administrative control over the entire server. Prevention techniques include using prepared statements (parameterized queries) and strictly validating all user input. 3. Database Transaction (ACID) A transaction is a single logical unit of work that performs one or more database operations (like a bank transfer) as a coherent whole. To guarantee reliability, transactions must follow the ACID properties: Atomicity: The "all-or-nothing" rule; the transaction either completes fully or fails entirely. Consistency: Ensures the database moves from one valid state to another, following all rules and constraints. Isolation: Prevents concurrent transactions from interfering with one another. Durability: Guarantees that once a transaction is committed, its changes are permanent, even in the event of a system crash. 4. PL/SQL (Procedural Language/SQL) PL/SQL is Oracle’s procedural extension to standard SQL, allowing developers to combine the data manipulation power of SQL with programming features like variables, loops, and conditional logic. It is organized into blocks (e.g., functions, procedures, and triggers) that are processed as a single unit by the database engine, which reduces network traffic and improves performance compared to executing individual SQL statements one at a time.