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laravel中的simplePaginate（进行一次查询完成分页）是怎么实现的？？

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laravel中的simplePaginate（进行一次查询完成分页）是怎么实现的？？

如图所示，打印laravel中simplePaginate用到的sql语句，它只用了一条sql。
但从结果上看，它可以判断下一页是否有数据，这是怎么做到的？
不计算总数，是怎么知道下一页还有没有数据的？
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by (71.8m points)

laravel的simplePaginate和paginate，传入的参数都是每页数量，但是实际上查询逻辑有区别

simplePaginate的需求简单，只生成上一页和下一页链接，所以用一条冗余查询(你打印的SQL中就可以看出是limit 3)来换取少一次查询，实际返回的结果还是你参数定义的每页数量

你再打印下paginate执行的SQL，你会发现是两条，一条count，一条实际查询


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