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Correct deep-pagination-optimization.md
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docs/high-performance/deep-pagination-optimization.md
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@ -64,12 +64,12 @@ SELECT * FROM t_order WHERE id > 100000 LIMIT 10
```sql
# 通过子查询来获取 id 的起始值，把 limit 1000000 的条件转移到子查询
SELECT * FROM t_order WHERE id >= (SELECT id FROM t_order limit 1000000, 1) LIMIT 10;
SELECT * FROM t_order WHERE id >= (SELECT id FROM t_order where id > 1000000 limit 1) LIMIT 10;
```
**工作原理**:
1. 子查询 `(SELECT id FROM t_order LIMIT 1000000, 1)` 会利用主键索引快速定位到第 1000001 条记录，并返回其 ID 值。
1. 子查询 `(SELECT id FROM t_order where id > 1000000 limit 1)` 会利用主键索引快速定位到第 1000001 条记录，并返回其 ID 值。
2. 主查询 `SELECT * FROM t_order WHERE id >= ... LIMIT 10` 将子查询返回的起始 ID 作为过滤条件，使用 `id >=` 获取从该 ID 开始的后续 10 条记录。
不过，子查询的结果会产生一张新表，会影响性能，应该尽量避免大量使用子查询。并且，这种方法只适用于 ID 是正序的。在复杂分页场景，往往需要通过过滤条件，筛选到符合条件的 ID，此时的 ID 是离散且不连续的。
@ -84,12 +84,12 @@ SELECT * FROM t_order WHERE id >= (SELECT id FROM t_order limit 1000000, 1) LIMI
-- 使用 INNER JOIN 进行延迟关联
SELECT t1.*
FROM t_order t1
INNER JOIN (SELECT id FROM t_order LIMIT 1000000, 10) t2 ON t1.id = t2.id;
INNER JOIN (SELECT id FROM t_order where id > 1000000 LIMIT 10) t2 ON t1.id = t2.id;
```
**工作原理**:
1. 子查询 `(SELECT id FROM t_order LIMIT 1000000, 10)` 利用主键索引快速定位目标分页的 10 条记录的 ID。
1. 子查询 `(SELECT id FROM t_order where id > 1000000 LIMIT 10)` 利用主键索引快速定位目标分页的 10 条记录的 ID。
2. 通过 `INNER JOIN` 将子查询结果与主表 `t_order` 关联，获取完整的记录数据。
除了使用 INNER JOIN 之外，还可以使用逗号连接子查询。
@ -97,7 +97,7 @@ INNER JOIN (SELECT id FROM t_order LIMIT 1000000, 10) t2 ON t1.id = t2.id;
```sql
-- 使用逗号进行延迟关联
SELECT t1.* FROM t_order t1,
(SELECT id FROM t_order limit 1000000, 10) t2
(SELECT id FROM t_order where id > 1000000 LIMIT 10) t2
WHERE t1.id = t2.id;
```