为什么带有子查询的MySQL LIMIT条件搜索比简单搜索快？

Question

Mentioned in Alibaba Java Code Convention , see https://yq.aliyun.com/articles/69327 Rule 3.2.7

SELECT a.* FROM table1 a, (SELECT id FROM table1 WHERE condition LIMIT 100000, 20) b WHERE a.id = b.id

is much faster than

SELECT * FROM table1 WHERE condition LIMIT 100000, 20

This article explains that MySQL will fetch 100020 result rows and eliminate first 100000 instead of only fetch 20 rows.

Is it true in MySQL query engine? May be a bug or defect?

UPDATE

assume table1 contains MANY columns (10+) and condition is not too complicated (eg ip LIKE '192.168.%' )

Answer 1

Yes, it's true.

The 1st query only scan 100020 result rows for field id then scan 20 rows full fields, but the second query scan 100020 for all fields.