Thuta Learning
Search
BasicData & Databasesbeginner

SELECT, Filtering, Sorting, and Pagination

Relax. We'll talk through this in plain words — no textbook voice.

What you'll walk away with

  • Explain the core ideas behind SELECT, Filtering, Sorting, and Pagination
  • Run the sample SQL or command and verify its output
  • Apply the technique to the Tutorial Platform and production scenarios

Build the mental model

SQL does not guarantee result order without `ORDER BY`. `LIMIT/OFFSET` is simple pagination, but large offsets become slow and concurrent inserts can cause duplicates or skipped rows. Use a stable tie-breaker, and prefer keyset pagination for large feeds.

Connect it to a real scenario

List published tutorials newest first, breaking equal timestamps by descending ID for deterministic results. Search input must be passed as a parameter by the application rather than concatenated into SQL. This lesson focuses on query semantics; the project chapter adds parameterization.

Try the working example

sql
-- First page
SELECT tutorial_id, title, published_at
FROM app.tutorials
WHERE is_published = true
ORDER BY published_at DESC, tutorial_id DESC
LIMIT 10;

-- Next keyset page: values come from the last visible row
SELECT tutorial_id, title, published_at
FROM app.tutorials
WHERE is_published = true
  AND (published_at, tutorial_id) <
      (TIMESTAMPTZ '2026-08-01 10:00:00+00', 42)
ORDER BY published_at DESC, tutorial_id DESC
LIMIT 10;
You should see
Published tutorials are returned in stable, page-sized batches.

5-minute try-it

Write a keyset-pagination query for active users ordered by creation time and ID.

One important caution

If the sort value is not unique and no unique tie-breaker exists, rows can disappear or repeat between pages.

PostgreSQL — Queries — PostgreSQL Global Development Group

Easy traps

  • If the sort value is not unique and no unique tie-breaker exists, rows can disappear or repeat between pages.
  • Validate sample code on a local or test database with recoverable backups before applying it to production data.

Exercise

Write a keyset-pagination query for active users ordered by creation time and ID.

You'll know it worked when: Published tutorials are returned in stable, page-sized batches.

SELECT, Filtering, Sorting, and Pagination | Thuta Learning