对于在外部表中找到的每一行，数据库服务器将在第二个(或内部)表中搜索其相应的行。

For every row found in the outer table, the database server searches for its corresponding row in the second (or inner) table.

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当使用外键时(ei列被存储在它们自己的表中)，可以在外键表中找到孤立的记录并将其转化为删除存根。

When external keys are in use (ei columns stored in their own table), we are able to find the orphaned record in the external key table and turn it into a deletion stub.

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通常情况下，在外部输入的基数显然不小且对于内部表没有一种有效的访问方法时，优化器会选择合并扫描联接。

Typically, the optimizer chooses merge scan join when the cardinality of the outer input is not obviously small and there is no efficient access method for the inner table.

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