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In this article Xiaobian for you to introduce in detail "what is the method of SQL code optimization", the content is detailed, the steps are clear, the details are handled properly, I hope this article "what is the method of SQL code optimization" can help you solve your doubts, the following follows the editor's ideas slowly in depth, together to learn new knowledge.

The way most people write it at present

After several times of REVIEW code, such phenomena are found as follows:

In the business code, you need to query whether there are records based on one or more conditions, regardless of how many records there are. The common SQL and code writing methods are as follows

# SQL:

SELECT count (*) FROM table WHERE a = 1 AND b = 2

# Java:

Int nums = xxDao.countXxxxByXxx (params)

If (nums > 0) {

/ / execute the code here when it exists

} else {

/ / execute the code here when it does not exist

}

Does it feel very OK? there is no problem.

Optimization scheme

It is recommended to write as follows:

# SQL:

SELECT 1 FROM table WHERE a = 1 AND b = 2 LIMIT 1

# Java:

Integer exist = xxDao.existXxxxByXxx (params)

If (exist! = NULL) {

/ / execute the code here when it exists

} else {

/ / execute the code here when it does not exist

}

SQL no longer uses count, but uses LIMIT 1 instead, so that when a database query comes across, it will be returned, and do not continue to find how many entries are left.

Directly judge whether it is not empty in the business code.

After reading this, the article "what is the method of SQL code optimization" has been introduced. If you want to master the knowledge of this article, you still need to practice and use it yourself. If you want to know more about the article, you are welcome to follow the industry information channel.

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