สอนพื้นฐาน SQL ทั้งหมดแบบจบในคลิปเดียว !! 🔥

Introduction

This tutorial provides a comprehensive guide to learning SQL from installation to mastering fundamental commands. Whether you are a beginner or have some knowledge of databases, this step-by-step guide will help you understand SQL and its practical applications.

Step 1: Understanding Databases and SQL

• Familiarize yourself with databases and their importance in storing and managing data.
• Learn about SQL (Structured Query Language) as the standard language for interacting with databases.
• Explore the internal structure of databases to understand how data is organized.

Step 2: Installing SQLite

• Download SQLite from the official website.
• Follow the installation instructions for your operating system.
• Verify the installation by running the SQLite command line interface.

Step 3: Basic SQL Structure and Commands

• Understand the basic structure of SQL commands.
• Familiarize yourself with key SQL commands, including:
  • SELECT
  • INSERT
  • UPDATE
  • DELETE

Step 4: Importing Database Files

• Learn how to import existing database files into SQLite for practice.
• Use the .import command to load data into your database.

Step 5: Using the SELECT Command

• Use the SELECT command to retrieve data from a database.
• Example syntax:

  SELECT * FROM table_name;
  

• Learn how to select specific columns:

  SELECT column1, column2 FROM table_name;
  

Step 6: Renaming Columns and Filtering Data

• Use the AS keyword to rename columns in your query results:

  SELECT column1 AS new_name FROM table_name;
  

• Apply the WHERE clause to filter results:

  SELECT * FROM table_name WHERE condition;
  

Step 7: Sorting and Limiting Results

• Sort results using the ORDER BY clause:

  SELECT * FROM table_name ORDER BY column_name ASC|DESC;
  

• Limit the number of results returned using LIMIT:

  SELECT * FROM table_name LIMIT number;
  

Step 8: Inserting, Updating, and Deleting Data

• Insert new data using the INSERT command:

  INSERT INTO table_name (column1, column2) VALUES (value1, value2);
  

• Update existing data with the UPDATE command:

  UPDATE table_name SET column1 = value1 WHERE condition;
  

• Delete data using the DELETE command:

  DELETE FROM table_name WHERE condition;
  

Step 9: Using Aggregate Functions

• Understand what aggregate functions are and how to use them.
• Use COUNT to count entries:

  SELECT COUNT(*) FROM table_name;
  

• Calculate averages and totals using AVG and SUM:

  SELECT AVG(column_name) FROM table_name;
  SELECT SUM(column_name) FROM table_name;
  

• Find maximum and minimum values with MAX and MIN:

  SELECT MAX(column_name) FROM table_name;
  SELECT MIN(column_name) FROM table_name;
  

Step 10: Grouping Data

• Group data using the GROUP BY clause:

  SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name;
  

• Use HAVING to filter grouped data:

  SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name HAVING COUNT(*) > value;
  

Step 11: Understanding SQL Operators

• Learn about common SQL operators such as:
  • NOT
  • IN
  • LIKE
  • BETWEEN
  • IS NULL
• Combine conditions using AND and OR.

Step 12: Joining Tables

• Understand different types of JOIN operations:
  • INNER JOIN
  • LEFT JOIN
  • RIGHT JOIN
  • FULL OUTER JOIN
• Example syntax for an INNER JOIN:

  SELECT columns FROM table1 INNER JOIN table2 ON table1.id = table2.id;
  

Step 13: Using CASE and Subqueries

• Use the CASE statement to create conditional logic in your queries:

  SELECT column_name,
         CASE
             WHEN condition THEN result1
             ELSE result2
         END
  FROM table_name;
  

• Learn how to write subqueries to retrieve data from multiple tables.

Conclusion

This tutorial has covered the essentials of SQL, from installation to advanced querying techniques. You can now practice these commands in SQLite, apply them in real-world scenarios, and explore further learning resources. Consider enrolling in courses to deepen your knowledge and earn certifications. Happy querying!