When only one person uses a database at a time, correctness is easy. Real systems, though, run many transactions at once, and the database interleaves their reads and writes to keep throughput high. That interleaving is where trouble starts: if two transactions touch the same rows at the wrong moments, one of them can read data that was never committed, see different values on repeated reads, or silently overwrite another user's work.
This topic gives names to those failures so you can recognize them precisely. A dirty read happens when a transaction reads uncommitted data that is later rolled back. A non-repeatable read occurs when a transaction re-reads a row and finds it changed. A phantom read occurs when a repeated query returns a different set of rows because another transaction inserted or deleted data matching the search condition. A lost update occurs when two transactions read the same value, each computes a new value, and the second write erases the first. Each of these is a specific pattern of interleaved operations, not a vague "bug" — and each one chips away at data integrity in ways that are hard to detect after the fact.
As you watch, focus on the timelines. Try to redraw each scenario as two columns, Transaction A and Transaction B, with the read, write, commit, and rollback steps in order, and mark the exact moment the anomaly becomes possible. Being able to produce that diagram from memory is the skill you will need later in the module when you choose isolation levels and concurrency control strategies.
A compact lecture that walks through the standard set of concurrency problems covered in database theory courses, including dirty read, lost update, incorrect summary (also called inconsistent analysis), and phantom read. The title indicates each problem is presented in turn, so expect short worked examples showing how two transactions interleave to produce each anomaly.
Gate Smashers is a widely used exam-preparation channel for DBMS topics, and this video is the most efficient single overview of the full anomaly catalog in under five minutes — a good first pass before you look at any one problem in depth.
This tutorial frames concurrency problems in the context of a specific commercial system, SQL Server, and pairs the problems with the mechanisms used to address them. Based on its description, it covers what happens when multiple users access the same data and how concurrency control is used to preserve consistency.
It bridges the abstract anomaly definitions to a real DBMS, which helps you see that these are practical engineering concerns rather than textbook curiosities, and it previews the control strategies examined later in the module.
A focused, longer treatment of a single anomaly: the dirty read. The description indicates it explains how a dirty read arises in SQL Server and how reading uncommitted data compromises data integrity, giving more room for setup, demonstration, and discussion than a survey video allows.
Dirty reads are the gateway concept for the whole topic, and spending nine minutes on one anomaly makes the underlying read-uncommitted-then-rollback sequence concrete in a way a quick summary cannot.
Together these videos target MO2 most directly: the Gate Smashers lecture names and distinguishes the full set of anomalies, while the dirty read video slows down on one case so you can trace the exact transaction interleaving that causes it. The SQL Server concurrency video extends that foundation toward MO3 and MO4 by connecting the anomalies to the isolation settings and control mechanisms a real engine provides, which is the vocabulary you will use when evaluating trade-offs between safety and performance. None of the three substitutes for the module readings on ACID properties (MO1) or deadlock handling (MO5), so treat them as the anomaly-identification layer of the module rather than complete coverage.
These videos were chosen from YouTube on October 2, 2026. Each has captions; the player turns them on. Videos on YouTube can be changed or removed — if one no longer plays, tell your instructor. If a player does not appear, use its Watch on YouTube link.