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devexamples

Optimistic Locking Update

Update a row only when its version still matches, detecting concurrent modification through the affected row count.

SqlData Integrity

Code

snippet
-- 乐观锁更新：版本匹配才写入，且不允许透支。
UPDATE accounts
SET balance = balance - :amount,
    version = version + 1
WHERE id = :account_id
  AND version = :expected_version
  AND balance >= :amount;

-- 应用侧检查受影响行数：
--   1  -> 更新成功
--   0  -> 并发冲突，或余额不足（需再读一次以区分）

-- 取回最新版本用于重试：
SELECT id, balance, version FROM accounts WHERE id = :account_id;

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