For an instructor lead, in-depth look at learning SQL click below.
Welcome to SQL made simple! No matter whether you’re new to SQL or need a refresher, this handbook will guide you through the basics and subtleties of SQL.
What is SQL?
SQL, or Structured Query Language, is a programming language specifically designed for managing and manipulating structured data stored in relational databases.
Basic SQL Queries
Let’s start with simple Select Queries, which are used to fetch data from a database:
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SELECT * FROM Customers; |
This query fetches_ all the data from the “Customers” table.
Filtering Data
You can filter your data using the WHERE clause. It’s like asking your database a question. For example, if you want to get all customers who live in New York:
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SELECT * FROM Customers WHERE city='New York'; |
This query fetches all records from the “Customers” table where the city column value is ‘New York’.
Combining Tables
To combine rows from two or more tables based on a related column between them, we use a JOIN:
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SELECT Orders.OrderID, Customers.CustomerName FROM Orders INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID; |
This SQL statement lists the OrderID and the name of the customer from the “Customers” and “Orders” tables where the CustomerID column in Orders is the same as the CustomerID in Customers.
Closing Thoughts
SQL is a powerful tool that can make your life significantly easier once you understand what it is, how it works, and what you can do with it. Practice is key in mastering SQL or any programming language. So, play around with these examples and come up with new queries to solidify your understanding.
Stay tuned for more articles on each of these areas and much more!