SQL Server外连接 [英] SQL Server Outer Joins

问题描述

1。是否真的可以说Full Outer Join总会返回与Left或Right Outer Join相同的行数？



2.完全外部用于你不知道（也不关心）两个表中哪一行有更多行的情况？相反，你需要所有匹配和不匹配的行吗？



3.或者当你必须外连接多个表（超过两个）时，Full Outer更有意义）？

1. Is it true to say that a Full Outer Join will always return the same amount of rows as either a Left or Right Outer Join?

2. Would a Full Outer to be used in situations where you didn't know (nor care) which of the two tables had the more rows? where instead you need all matching and non-matching rows regardless?

3. Or do Full Outer's make more sense when you have to outer join multiple tables(more than two)?

推荐答案

有一个很好的例子这里 [ ^ ]。它应该有帮助。

There is a good example here[^]. It should help.

检查此链接

SQL连接的可视化表示 [ ^ ]

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