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MySQL how to optimize non-indexed join, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain in detail for you, people with this need can come to learn, I hope you can gain something.

Preface

Have you ever used MySQL Join? Do you know how it works?

Now there is a user table, and this user table is very simple, with a primary key id, our user id, and a name field, which is obviously the user's name.

At this time, there is also a user_info table, this user_info table stores some other information about the user, there is an id that user_id represents the user, and an account represents the deposit of the user.

Ergodic circular query

If we want to find out the names and deposits of all users, we can look it up like this:

Data = select * from user;for

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