Working with Single-Table Data

Overview

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In the previous part, we practiced reading database structure and asking what kinds of questions a schema could support. In this part, we continue with that same idea, introducing the concrete tool used to express many of those questions: Structured Query Language (SQL).

SQL is a language for asking a database for data and for changing stored data. In this part, we work with one table at a time so that the basic query and data-modification patterns become familiar before relationships make the questions more complex. By the end of the part, you should be able to read a table, connect a question to that table, write simple queries, and make changes to the data in the database in a controlled way.

Later parts use SQL in several ways, including reading data, modifying data, and defining or changing schema structure. For now, the focus stays on simple one-table work.

As in the previous part, we’ll have two recurring contexts. Some chapters focus on SQL itself through smaller one-table examples, while the study tracker project continues as the long-running project track.

The structure of this part is as follows:

• From Schema to Query starts with basic SELECT queries and reading data from one table.
• Filtering With WHERE shows how to select only the rows that matter for a question.
• Working With NULL explains missing values and how SQL treats them.
• Sorting and Limiting Results introduces result ordering, limiting, and a few common result-shaping patterns.
• Simple Expressions in Queries shows how to compute values and rename columns inside a query.
• Inserting Data introduces adding new rows to a table.
• Updating and Deleting Data discusses careful row changes and controlled deletion.
• Debugging SQL Queries presents practical habits for checking what a query actually does.
• Project Checkpoint first uses direct SQL on the Part 1 project database and then adds one small scaffolded read-only feature to the same study tracker project.

The SQL Quick Reference is a useful companion for this part. It does not replace the chapters, but it helps when you want to check the basic shape of a statement quickly.

Recommended Order of Work

A useful rhythm for this part is:

1. read the regular chapters in order,
2. complete the chapter-level exercises as you go,
3. then complete the part’s project checkpoint,
4. and finish with the recap quiz and feedback form.

Finally, at the end of the part, there is a recap and feedback chapter that briefly summarizes the part and asks for feedback.