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This article mainly introduces the example analysis of exists and not exists in mysql, which has a certain reference value, and interested friends can refer to it. I hope you will gain a lot after reading this article.

This article mainly introduces the relevant information about the detailed explanation of mysql exists and not exists examples. In view of the fact that the efficiency of not exists is often higher than that of not in, the former is usually used instead of the latter. Friends in need can refer to it and hope to help you.

TableA

| | column1 | column1 | column3 | |

Tableb

| | column1 | column1 | column3 | |

To query the data of tableA, the condition is that tableA.column1 is not in tableB's tableB.column2

That is, to get an effect similar to the following statement (the not in effect is not exactly the same as not exists, if an empty record appears in the subquery, the whole query statement will not return data)

SELECT a.*FROM tableA aWHERE a.column1 not in (SELECT column2 FROM tableB)

You can use the following statement to implement the

SELECT a.*FROM tableA aWHERE NOT EXISTS (SELECT b.column2 FROM tableB b WHERE a.colunm1=b.column2) Thank you for reading this article carefully. I hope the article "sample Analysis of exists and not exists in mysql" shared by the editor will be helpful to you. At the same time, I also hope you will support us and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

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