For an instructor lead, in-depth look at learning SQL click below.
Welcome to the realm of SQL! SQL, standing for Structured Query Language, is a programming language used to communicate with and manipulate databases. This guide is meant to be a one-stop-shop for newcomers who are eager to learn SQL basics. Let us get the ball rolling!
What is SQL?
SQL, pronounced “sequel,” is a language designed to allow both technical and non-technical users to do various tasks, ranging from querying data, to creating and modifying databases, with relative ease. A powerful feature of SQL is that it can work with vast amounts of data, stored in a type of database called relational databases.
Writing Basic SQL Queries
At its core, you need to remember the purpose of SQL: to communicate with databases. The most common command used in SQL is the SELECT statement. This command is used when you want to retrieve data from your database. Let’s look at an example:
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SELECT * FROM Employees; |
In this example, the SQL statement says ‘SELECT all records FROM the Employees table.’ The asterisk is a wildcard character in SQL and represents ‘all columns’.
SQL WHERE Clause
Often, we have specific criteria we need to meet when pulling data. This is where the WHERE clause comes into play. The WHERE clause helps to extract only those records that fulfill a specified condition. Let’s modify the previous example to only pull employees who work in ‘Sales’ department. Here’s how you would write that:
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SELECT * FROM Employees WHERE department = 'Sales'; |
SQL JOIN
Next up, let’s tackle a cornerstone task in SQL, joining tables. This becomes essential when you want to combine rows from two or more tables, based on a related column. There are several types of JOIN statements, but for this beginner’s guide, we’ll cover the INNER JOIN.
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SELECT Employees.employee_name, Sales.sale_amount FROM Employees INNER JOIN Sales ON Employees.employee_id = Sales.employee_id; |
This will give you a list of all employees and their respective sales amounts, but only for those employees who have made at least one sale.
By mastering these basics, you’ll be well on your way to becoming proficient in SQL. Remember, practice makes perfect – the more queries you write, the better you’ll get at it.
Conclusion
We hope this beginner’s guide has helped you understand the basics of SQL and has kick-started your learning journey. Database interrogation using SQL is one of the most valuable skills anyone working with data can have. Keep practicing and happy querying!