📘 SQL Basics — Everything You Should Know

1️⃣ Database Basics

• 📂 What is a database?
• 🧱 SQL introduction
• 🏗 Types of database objects: Tables, Views, Indexes, Sequences, Triggers

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2️⃣ SQL Categories

• 🧱 DDL – CREATE, ALTER, DROP, TRUNCATE
• ✏️ DML – INSERT, UPDATE, DELETE
• 🔍 DQL – SELECT
• 🔒 TCL – COMMIT, ROLLBACK, SAVEPOINT
• 🔐 DCL – GRANT, REVOKE

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3️⃣ Basic Queries

• Filtering: WHERE, BETWEEN, IN, LIKE, IS NULL
• Sorting: ORDER BY
• Limiting: LIMIT
• Logical operators: AND, OR, NOT
• Conditional logic: CASE

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4️⃣ Functions

🔢 Aggregate Functions

SUM, AVG, COUNT, MAX, MIN

🔤 String Functions

CONCAT, LENGTH, SUBSTRING, UPPER, LOWER, TRIM

📅 Date Functions

NOW(), CURDATE(), DATE_ADD(), DATE_FORMAT()

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5️⃣ Grouping & Filtering Groups

• GROUP BY → group rows
• HAVING → filter groups after grouping

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6️⃣ Joins

• 🔗 INNER JOIN
• ↪️ LEFT JOIN
• ↩️ RIGHT JOIN
• 🌐 FULL JOIN
• 🔁 SELF JOIN
• ❌ CROSS JOIN

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7️⃣ Constraints

• 🔑 PRIMARY KEY
• 🔗 FOREIGN KEY
• 🆔 UNIQUE
• 🚫 NOT NULL
• ✔️ CHECK
• 📌 DEFAULT

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8️⃣ Set Operations

• UNION
• UNION ALL
• INTERSECT
• EXCEPT (if supported)

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9️⃣ Transactions & TCL

• 🧪 START TRANSACTION
• 💾 COMMIT
• ❌ ROLLBACK
• 🧩 SAVEPOINT

Ensures ACID properties (Atomicity, Consistency, Isolation, Durability)

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🔟 Index

• ⚡ CREATE INDEX → improves search speed
• Can be: Unique or Non-Unique

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🚀 Advanced SQL — Level Up Your Database Skills 1️⃣ Subqueries & Nested Queries

🔍 Subquery in WHERE

📦 Subquery in FROM (derived table)

🎯 Subquery in SELECT

🔁 Correlated Subqueries

⚡ EXISTS vs IN vs ANY vs ALL

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2️⃣ Advanced Joins

👥 Self Join (manager-management table)

🔗 Multi-table joins

📊 Joins with Aggregate Functions

🔄 Cross Join usage in real cases

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3️⃣ Views

🪟 Creating views: CREATE VIEW

🔄 Updating data with views

🚫 Updatable vs Non-Updatable Views

📘 Real use cases: security, simplification

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4️⃣ Stored Procedures & Functions

⚙️ CREATE PROCEDURE

🧵 Input & Output parameters

🔄 CALL a procedure

📌 Stored Functions using RETURN

🔁 Reusable logic for apps

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5️⃣ Triggers

🧨 BEFORE INSERT

🔥 AFTER UPDATE

📘 Auditing tables

📝 Logging data changes

⚠️ Enforcing rules automatically

6️⃣ Window Functions (Analytical Functions)

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🪟 ROW_NUMBER()

🎖 RANK()

🥇 DENSE_RANK()

⏭️ LEAD()

⏮️ LAG()

➕ Running totals → SUM() OVER()

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7️⃣ CTE — Common Table Expressions

📄 WITH clause

🔁 Recursive CTE

Organization hierarchy

Category trees

Explaining parent-child relations

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8️⃣ Indexing (Performance Boost)

⚡ Composite Index

📘 Covering Index

🧱 Clustered vs Non-Clustered (conceptual)

🚀 How indexes affect WHERE, JOIN, ORDER BY

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9️⃣ Normalization & Design

1️⃣ 1NF

2️⃣ 2NF

3️⃣ 3NF

🔵 BCNF

🧩 When to use Denormalization

📦 Data redundancy control

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🔟 Query Optimization

🔍 EXPLAIN — read query execution plan

⚙️ Optimizing joins

🧹 Avoiding heavy subqueries

🚅 Improving performance using indexes

📉 Avoid full table scans