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Differences between on and where filtering in mysql left join

Join also supports multiple conditions

There is the ON keyword, which is equivalent to the where keyword for left outer join query

It’s in-depth, I learned it in passing

table1 left join table2 on + 查詢條件. You need to learn more SQL statements, the foundation is not solid enough...

Correct answer upstairs, the poster needs to read more about the basics

This and is connected with the condition after on, and is one of the conditions associated with the table. Basics............

1. Join on followed by the and condition is the condition used when generating a temporary table. It will return the records in the left table regardless of whether the condition in on is true.

2. The where condition is the condition for filtering the temporary table after the temporary table is generated. At this time, there is no meaning of left join (the records of the left table must be returned). If the condition is not true, all will be filtered out.

The basic part of SQL language includes inner joins, outer joins, and outer joins are divided into left outer joins, right outer joins, and complete outer joins. You can find it by looking at the basics of SQL language