Subject : Various JOINs of MySQL
Outline :
1. Teacher Xu has been engaged in official MySQL work for many years, and when he provides MySQL help to many companies, what are the issues that companies are more concerned about?
2. With the maturity and promotion of MySQL 8.0, I believe that more and more companies want to upgrade MySQL 8.0, but they are worried about whether there will be compatibility issues with the upgrade from lower version to higher version. Can Mr. Xu share relevant experience?
3. Teacher Xu brought the wonderful content of JOIN in this theme. Compared with MySQL 5.7, what aspects of JOIN enhanced in MySQL 8.0?
4. Too much "left join" often results in slow SQL performance. Can you share your suggestions or precautions for "left join"?
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Guests introduce themselves
Xu Yitao , Senior Engineer of MySQL Solutions
Oracle's MySQL solution engineer, providing MySQL-related products pre-sale consultation, enterprise-level product introduction services, and promotion and popularization of the use of MySQL database in the community for MySQL users in China and Northeast Asia
01
Teacher Xu has been engaged in official MySQL work for many years, and when he provides MySQL help to many companies, what are the issues that companies are more concerned about?
There are three main issues that enterprises are more concerned about:
1. Can you be guaranteed in the process of using the software? How to provide protection? What degree of protection can be provided?
2. Data security.
3. Use software in compliance.
02
With the maturity and promotion of MySQL 8.0, it is believed that more and more companies want to upgrade MySQL 8.0, but they are worried about whether there will be compatibility issues with the upgrade from lower version to higher version. Can Mr. Xu share relevant experience?
Any software upgrade will have compatibility issues. Be sure to check the release announcement of the new software before upgrading. If it is confirmed that it will not affect the existing system, follow the official recommended method to upgrade step by step. If there are some conflicts, you should resolve the conflicts before upgrading. For a database system, it must be fully tested before it can be used in a production environment.
03
Teacher Xu's topic this time brings the wonderful content of JOIN. Compared with MySQL 5.7, what aspects of JOIN are enhanced in MySQL 8.0?
8.0 mainly adds hash JOIN in the algorithm, and has made certain optimizations in anti-join, semi-join, etc.
04
Excessive "left join" often results in slow SQL performance. Can you share your suggestions or precautions for "left join"?
Reduce excessive left join????, decompose the query, and use the application cache. Unlike inner joins, which can change the order of tables, optimization is relatively complicated. It is recommended that you master various algorithms used by the optimizer, adjust queries, and output results as expected.
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