Select without the order by clause, the order of the returned results is not reliable

Catalog

Preface

One 、select Sentence without order by Clause , The return result is uncertain ？

Two 、 Use steps

1. Query statement

2. Add order by Query statement

summary

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Preface

Recent project design to the relocation of localization environment , Today, I tested the function of the migrated Jincang database , serendipity select If you do not add order by Statement specifies the collation , Then the order of its query results is unreliable , At first, I thought it was the reason for the Jincang database of NPC , Later, after reading the information, I learned that select If not order by Clause , The order of the returned results is unreliable . Its storage engine , Has it been migrated , modify , And adding and whether there is an index will affect the order of results .

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Tips ： The following is the main body of this article , The following cases can be used for reference

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One 、select Sentence without order by Clause , The return result is uncertain ？

Again, don't do too many demonstrations , Those who are interested can observe by themselves .

Two 、 Use steps

1. Query statement

The code is as follows （ Example ）：

select * from student

2. Add order by Query statement

The code is as follows （ Example ）：

select * from student order by id

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summary

because select Sentence without order by Clause , The order of query results is unreliable , So you want to sort , Always add order by Of .