Learn Basic SQL in 15 Minutes | Business Intelligence For Beginners | SQL Tutorial For Beginners 1/3

Introduction

This tutorial will guide you through the basics of SQL, focusing on essential queries that you'll need for Business Intelligence (BI). In just 15 minutes, you will learn how to retrieve and manipulate data from databases, a crucial skill for aspiring BI analysts. The concepts covered here can be applied across various SQL platforms like MySQL, PostgreSQL, and SQL Server.

Step 1: Understanding the SQL SELECT Statement

• The SQL SELECT statement is used to select data from a database.
• Basic syntax:

  SELECT column1, column2 FROM table_name;
  

• Replace column1, column2, and table_name with your actual column and table names.

Step 2: Using AS for Field Aliasing

• Field aliasing allows you to rename columns in your result set for better readability.
• Syntax for aliasing:

  SELECT column_name AS alias_name FROM table_name;
  

• Example:

  SELECT first_name AS Name FROM employees;
  

Step 3: Filtering Data with the WHERE Clause

• The WHERE clause filters records based on specified conditions.
• Basic syntax:

  SELECT column1, column2 FROM table_name WHERE condition;
  

• Example:

  SELECT * FROM employees WHERE department = 'Sales';
  

Step 4: Sorting Results with ORDER BY

• The ORDER BY clause is used to sort the result set in ascending or descending order.
• Syntax:

  SELECT column1, column2 FROM table_name ORDER BY column_name ASC|DESC;
  

• Example:

  SELECT * FROM employees ORDER BY last_name ASC;
  

Step 5: Joining Tables with INNER JOIN

• INNER JOIN combines rows from two or more tables based on a related column.
• Basic syntax:

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

• Example:

  SELECT employees.first_name, departments.department_name 
  FROM employees 
  INNER JOIN departments ON employees.department_id = departments.id;
  

Step 6: Aliasing Tables

• You can also alias tables for easier reference in queries.
• Syntax:

  SELECT a.column1, b.column2 
  FROM table1 AS a 
  INNER JOIN table2 AS b ON a.id = b.id;
  

Step 7: Grouping Data with GROUP BY

• The GROUP BY clause groups rows that have the same values in specified columns into summary rows.
• Syntax:

  SELECT column1, COUNT(*) FROM table_name GROUP BY column1;
  

• Example:

  SELECT department, COUNT(*) FROM employees GROUP BY department;
  

Step 8: Filtering Grouped Data with HAVING

• The HAVING clause is used to filter records that work on summarized group data.
• Syntax:

  SELECT column1, COUNT(*) FROM table_name GROUP BY column1 HAVING COUNT(*) > value;
  

• Example:

  SELECT department, COUNT(*) FROM employees GROUP BY department HAVING COUNT(*) > 10;
  

Conclusion

In this tutorial, you learned the foundational elements of SQL, including SELECT statements, aliases, the WHERE clause, sorting results, joining tables, grouping data, and filtering grouped data. These skills are essential for analyzing data in any BI role. To enhance your SQL knowledge, consider exploring more advanced topics or enrolling in a comprehensive SQL course. Happy querying!