Advanced Reporting

Locking and Deadlocks

Senior Data Analyst
March 29, 2026
5 min read

The Problem

Transaction A locks Row 1 and waits for Row 2. Transaction B locks Row 2 and waits for Row 1. They wait forever—a **Deadlock**.

How Databases Handle It

The database detects the deadlock and automatically kills one transaction.

Prevention

  • Access tables in a consistent order.
  • Keep transactions short.
  • Use `SELECT ... FOR UPDATE` carefully.

    • *Day 89: Error Handling in SQL.*

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