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How to use exists in oracle

angryTom

Mar 06, 2020 pm 05:56 PM

existsoracleusage

How to use exists in oracle

Usage of exists in oracle

1. exists is followed by a subquery

How to use exists in oracle

2. The following two tables are used as examples to demonstrate that the id in table a is associated with the aid in table b

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How to use exists in oracle

3. The function of exists is to check whether the result of the subquery is true. If the subquery is true, the outer SQL statement is executed. exists does not return data and only returns true or false

How to use exists in oracle

##4. If it returns false, the external SQL statement will not be executed as shown below

How to use exists in oracle

5. Its usage is somewhat similar to in, but sometimes the efficiency is different when the amount of data is relatively large, but the efficiency is the same when the amount of data is relatively small.

How to use exists in oracle

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