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Feb 21, 2022 · Databases

Why Updating Non‑Indexed Columns Can Lock the Whole Table in MySQL

Through a series of MySQL 5.7.26 experiments the article reveals how record‑level locks are applied to primary‑key indexes when non‑indexed columns are locked, how isolation levels (READ COMMITTED vs REPEATABLE READ) change the locking order, and why both SELECT … FOR UPDATE and UPDATE statements can block other transactions.