Databases and SQL I · Lesson 03 / 12

Query with intent

Use SELECT, aliases, ORDER BY and LIMIT with explicit criteria.

Let's discover together

1
SELECT chooses expressions and FROM names the source. SELECT * helps exploration; reports should list necessary columns. This reduces noise and unnecessary data exposure.
2
Without ORDER BY, do not rely on row order. stock DESC and id ASC break ties. LIMIT 2 limits rows; by itself it does not pick the two most relevant records.
3
AS labels output without changing stored columns. stock * 2 AS planned calculates a hypothesis; it does not double stock. Distinguish stored facts from calculations in report names.
4
Predict ids, run and change DESC to ASC. Query stock again to confirm SELECT changed no values. Add a tie breaker when the first column may repeat.

Your data workbench

Our model: kits.id ← loans.kit_id. One material can have many loans; names may repeat. We use fictional data only.

Predict before opening the reference. It shows verified output from the original example, not execution of your text. Run your changes with the kit on your computer.

-- Query with intent
SELECT id, label, stock * 2 AS planned FROM kits ORDER BY stock DESC, id ASC LIMIT 2;

Compare with reference output

[
  {
    "columns": [
      "id",
      "label",
      "planned"
    ],
    "rows": [
      [
        1,
        "Orbit",
        6
      ],
      [
        2,
        "Sprout",
        4
      ]
    ]
  }
]

Run the command in the extracted folder’s terminal. Use python3 on macOS/Ubuntu or py if that is your Windows launcher. Every run starts in memory; read README.md for saving files and recovery practice.

python lab.py run lesson.sql

My files and GitHub

The editor saves your .sql draft in this browser. Download it and replace lesson.sql in the kit; for the final project, availability.sql. The ZIP remains the original template. GitHub publishing sends only the confirmed file, without executing SQL or sending a database.

Official links and next step

Official documentation

✦

YOUR MISSION

Use SELECT, aliases, ORDER BY and LIMIT with explicit criteria.

Take it with you

List three materials by name and id showing only code and label. Explain tie breaking.

At your own pace

My files and GitHub

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Student guide

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Your path, step by step

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Download the lesson example and a workbook for your notes. The ZIP includes a guide to organizing activities in one or more repositories. Publishing is optional; eligible accounts can also use the GitHub upload button.

Your file for this lesson

Edit the example or record what you learned. This space does not run code or grade answers. The draft is saved only in this browser, separately per account; you choose when to download or upload to GitHub.

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My code or notesFile format

Your text will be saved in this browser when you edit it. On a shared computer, clear your drafts when finished.

Direct upload accepts up to 8 KiB of text in one file. Use downloads and the manual guide for projects with multiple files.

Query with intent

Let's discover together

Your data workbench

Official links and next step

Now it's your turn

Read, predict and check

Take it with you

My files and GitHub

Your file for this lesson

Save to my GitHub

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