Introduction to DQL

Imagine our OnlineStore is planning a targeted marketing campaign. To do this effectively, we first need to understand our customers: Who are they? Where are they located? What are their buying habits? Similarly, to manage inventory, we need to know which products are low in stock or what our best-selling items are. How do we get this information from our database? This is where data query language (DQL) comes into play! It’s the set of SQL commands we use to ask our database questions and retrieve the specific information we need. Without DQL, all the valuable data we’ve carefully stored would be locked away and unusable for decision-making. This lesson will introduce you to the fundamentals of DQL, empowering you to unlock the stories hidden within your data.

By the end of this lesson, we will be able to:

• Understand the purpose and importance of data query language (DQL) in database management.

• Learn the basic structure of the SELECT statement.

• Retrieve all columns from a table.

• Retrieve specific columns from a table.

• Write and execute simple queries to fetch data from the OnlineStore database

What is data query language (DQL)?

In our journey as Database Administrators, we’ve learned how to create databases, manage users, and define the structure of our tables. But what’s the use of storing all this data if we can’t retrieve it when we need it? DQL is arguably the most frequently used part of SQL because it allows us to ask questions and fetch data from our database. Whether it’s generating reports, providing data for applications, or performing ad-hoc analysis, DQL is the tool we use to interact with and extract meaningful information from the vast amounts of data stored. For an online ...