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Database Deadlocks: Causes, Examples, and Solutions

Database deadlocks can occur when two transactions lock resources the other requires, creating a loop of dependencies. This article highlights the basics of deadlocks, offering straightforward solutions and examples to help prevent them.

Imagine three friends—Jack, William, and James—each waiting on another. In databases, similar conflicts can arise as follows.

START TRANSACTION;
UPDATE `demo_table` SET `username` = "Demo" WHERE `id` = 1;

START TRANSACTION;
UPDATE `demo_table_2` SET `username` = "Demo" WHERE `id` = 1;
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These updates result in a deadlock error.

ERROR 1213 (40001): Deadlock found when trying to get lock; try restart transaction.
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FAQ

What is a deadlock in databases?
Deadlocks happen when transactions wait on each other for resources, leading to a halt.

How can I prevent deadlocks?
Reduce resource locks in transactions, use efficient queries, and limit dependencies.

Do all databases detect deadlocks?
Some databases have built-in detection, but avoidance is often better than reliance on detection.

Are deadlocks completely preventable?
While rare, deadlocks can occur in high-load systems; thoughtful design helps minimize them.

Summary

Understanding and managing deadlocks is essential for smooth database operations. Discover more about deadlocks and practical solutions in the full article Deadlocks in Databases: A Guide.

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