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- LEFT JOIN vs. LEFT OUTER JOIN in SQL Server 12 answers
What is the difference between Left Join and Left Outer Join?
They are the same thing in MySQL. A LEFT JOIN is a synonym or shorthand for LEFT OUTER JOIN.
There is none. The keyword OUTER is optional. They mean the same.
来源:https://stackoverflow.com/questions/2809594/how-can-we-differ-left-outer-join-vs-left-join