For an instructor lead, in-depth look at learning SQL click below.
If you’re a beginner looking to master SQL, you’ve come to the right place. SQL, or Structured Query Language, is a language designed to manage and manipulate databases. SQL may seem complex at first, but with practice, you’ll be writing queries with ease.
The Basics of SQL
Before we start writing queries, let’s understand some fundamentals. SQL operates through declarative statements. This means, rather than telling the system how to get your data, you specify what data you need, and SQL works out the best way to deliver it.
At the heart of SQL is the statement “SELECT * FROM table_name.” Let’s break it down:
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SELECT * FROM table_name; |
In this code, “SELECT” is a clause that indicates you’re retrieving data. The “*” symbol signifies that you want all columns from the data source. “FROM” specifies from where to pull the data; this is usually followed by the table name.
Your First SQL Query
Let’s say we have a table named ‘Employees’ with data about a company’s employees. Our table looks like this:
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CREATE TABLE Employees ( ID INT PRIMARY KEY, Name VARCHAR (100), Role VARCHAR (100), Salary FLOAT); |
If we wanted to select all columns from the ‘Employees’ table, our query would look like this:
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SELECT * FROM Employees; |
Filtering and Sorting Data
As your data grows, you’ll need to filter and sort information. The WHERE and ORDER BY clauses can help you specify the data you’re looking for and the order in which you want to view it.
Let’s say we want to find out the details of employees whose salary is greater than $50000. Our query would look like this:
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SELECT * FROM Employees WHERE Salary > 50000; |
And if we wanted to sort these employees by their names in ascending order, we would use the ORDER BY clause like this:
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SELECT * FROM Employees WHERE Salary > 50000 ORDER BY Name ASC; |
Conclusion
There’s much more to SQL than the basics covered here, and as you continue practicing and working with queries, you’ll discover the immense power and flexibility this language offers in handling data. Happy querying!