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This article mainly shows you "Mysql can not select non-aggregate column how to do", the content is easy to understand, clear, hope to help you solve doubts, the following let the editor lead you to study and learn "Mysql can not select non-aggregate column how to do" this article.

1. Preface

Two buttons have been added to the bottom of the article page to jump directly to the previous and next posts.

As shown in the following figure:

The difficulty in achieving this function is: how does the database select two adjacent records before and after a record?

two。 Database design

The design of my article database is shown in the following figure:

As you can see, the identity of each record is index Id. Because many previous article records have been deleted, Id is not continuous.

If the index value of the current article is 33, you can get two adjacent articles with the following command:

Select * from passage where id in (selectcasewhen SIGN (id-32) > 0 THEN MIN (id) when SIGN (id-32)

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