mybatis 一对多 pagelper 分页问题

最新推荐文章于 2025-03-13 18:47:56 发布

原创最新推荐文章于 2025-03-13 18:47:56 发布 · 301 阅读

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#mybatis

本文探讨了在进行SQL查询时如何避免n+1查询问题，介绍了不使用PageHelper插件进行分页查询的方法，通过LIMIT关键字直接在主表查询中限制返回的记录数，以提高数据库查询效率。

SELECT
	goods.id,
	goods.goods_no,
	goods.goods_img,
	goods.goods_sale,
	goods.goods_title,
	goods.create_time,
	goods.update_time,
	goods.category_one,
	goods.category_two,
	goods.goods_content,
	goods.goods_sort,
	goods.goods_state,
	goods.goods_recommend,
	goods.version,
	banner.id AS banner_id,
	banner.goods_id AS banner_goods_id,
	banner_uri,
	spec.id AS spec_id,
	spec.goods_id AS spec_goods_id,
	spec.spec_img,
	spec.spec_name,
	spec.spec_title,
	spec.spec_price,
	spec.spec_stock,
	ca. NAME AS category_one_name,
	two. NAME AS category_two_name
FROM
	(
		SELECT
			*
		FROM
			goods_info
		LIMIT 0,
		10
	) goods
LEFT JOIN goods_banner banner ON goods.id = banner.goods_id
LEFT JOIN goods_spec spec ON goods.id = spec.goods_id
LEFT JOIN goods_category ca ON goods.category_one = ca.id
LEFT JOIN goods_category two ON goods.category_two = two.id

ORDER BY
	goods.goods_sort DESC

简单来说,不推荐使用collection里面的select查询会造成n+1性能以及内存问题

难么就不使用pagehleper插件了

自己写limit 查询主表的时候

具体的详细等后面有时间了再写吧

这里做一个简单记录

后面有时间写写原因啥的

看懒不懒了