Databases and SQL I · Lesson 05 / 12

Insert and respect constraints

Insert with explicit columns and diagnose constraint violations.

Let's discover together

1
INSERT INTO table (columns) VALUES (values) makes mappings explicit. Avoid relying on every column’s order. Text uses single quotes; apostrophes in handwritten literals are doubled. Applications should parameterize input, as we will see.
2
The example inserts Echo with valid zero stock. Repeating R-01 violates UNIQUE. A missing kit_id violates the foreign key: the runner enables foreign_keys on each connection instead of assuming SQLite defaults.
3
Check the rule named in the error and correct input. Do not switch to a conflict-removing operation without understanding consequences. The database enforces rules; an application must still explain errors usefully.
4
Each run starts from the initial schema. Put INSERT and SELECT in the same file to query an insertion. Saving lesson.sql saves instructions, not in-memory rows.

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.

-- Insert and respect constraints
INSERT INTO kits (id, code, label, category, stock) VALUES (5,'X-01','Echo','paper',0);
SELECT id, label, stock FROM kits WHERE id=5;

Compare with reference output

[
  {
    "columns": [
      "id",
      "label",
      "stock"
    ],
    "rows": [
      [
        5,
        "Echo",
        0
      ]
    ]
  }
]

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

Insert with explicit columns and diagnose constraint violations.

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Insert a valid object and test two violations separately. Record input, rule and result, including expected errors.

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Insert and respect constraints

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

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