For an instructor lead, in-depth look at learning SQL click below.
Welcome! If you’re new to SQL or looking to strengthen your understanding, you’re in the right place. SQL, Structured Query Language, is a programming language often used to manage data stored in relational databases. This beginner’s guide will illustrate the basics, led by helpful examples.
What is SQL?
SQL is a domain-specific language used in programming and designed for managing data held in a relational database management system or for stream processing in a relational data stream management system.
Getting Started with SQL
The most basic function of SQL is to select data from a database. It’s so fundamental that it’s often the first command people learn. Here’s the SQL statement that would allow you to retrieve all data from a data table:
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SELECT * FROM employees |
Fetch specific data with SQL
If we’re interested in more specific information, we can use a conditional statement. For example, if we only want to retrieve employees who have a salary greater than $50,000, we would use the following SQL command:
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SELECT * FROM employees WHERE salary > 50000 |
SQL Functions
SQL functions are powerful under the hood aids that help us manipulate and process data. Some popular functions include SUM(), AVG(), COUNT() and many more. Let’s compute the average salary in our employee database, for that we would use the AVG() function:
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SELECT AVG(salary) FROM employees |
Sorting Results in SQL
We can use the ORDER BY clause to sort our results. For example, if we want to sort employees based on their salaries in descending order, we can do as follows:
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SELECT * FROM employees ORDER BY salary DESC |
And that’s your introduction to SQL! While there’s lots more to learn, these basics will get you started on your journey. Happy coding!