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@ -353,14 +353,14 @@ SELECT c FROM t WHERE c BETWEEN 10 and 20 FOR UPDATE;
### Next-Key Locks
它是 Record Locks 和 Gap Locks 的结合，不仅锁定一个记录上的索引，也锁定索引之间的间隙。它锁定一个前开后闭区间，例如一个索引包含以下值：10, 11, 13, and 20，那么就需要锁定以下区间：
它是 Record Locks 和 Gap Locks 的结合，不仅锁定一个记录上的索引，也锁定索引之间的间隙。它锁定一个前开后闭区间，例如一个索引包含以下值：10, 11, 13, and 20，那么就需要锁定以下区间（其中 supremum 是一个不存在的最大值代表闭区间）：
```sql
(-∞, 10]
(10, 11]
(11, 13]
(13, 20]
(20, +∞)
(20, +supremum]
```
## 七、关系数据库设计理论