SQL For Data Queries

🔹 Introduction to SQL What is SQL (Structured Query Language)? Types of SQL commands: DDL, DML, DCL, TCL Overview of relational databases and tables 🔹 Basic SQL Syntax Writing SQL queries Case sensitivity and formatting Comments in SQL 🔹 Data Retrieval SELECT statement basics Selecting specific columns Selecting all columns (SELECT *) Using DISTINCT to get unique values 🔹 Filtering Data WHERE clause Operators: =, !=, <, >, <=, >= Logical operators: AND, OR, NOT Using BETWEEN, IN, LIKE (wildcards %, _) 🔹 Sorting and Limiting Data ORDER BY clause (ascending/descending) LIMIT or TOP to restrict rows 🔹 Aggregate Functions COUNT(), SUM(), AVG(), MIN(), MAX() Using GROUP BY for aggregation HAVING clause to filter grouped data 🔹 Joins Understanding table relationships INNER JOIN LEFT JOIN / LEFT OUTER JOIN RIGHT JOIN / RIGHT OUTER JOIN FULL JOIN / FULL OUTER JOIN Self joins 🔹 Modifying Data INSERT INTO for adding records UPDATE for modifying records DELETE for removing records 🔹 Creating and Modifying Tables CREATE TABLE syntax Defining columns and data types Primary keys and constraints (NOT NULL, UNIQUE) ALTER TABLE to add/drop/modify columns DROP TABLE to delete tables 🔹 Data Types in SQL Numeric types (INT, FLOAT, DECIMAL) String types (CHAR, VARCHAR, TEXT) Date and time types (DATE, TIME, DATETIME) 🔹 Constraints and Indexes Primary key Foreign key Unique constraint Default values Index basics 🔹 Subqueries and Nested Queries What is a subquery? Using subqueries in SELECT, WHERE, and FROM clauses 🔹 SQL Best Practices Writing readable and maintainable queries Using aliases (AS) Avoiding SQL injection basics