嵌套循环连接（Nested Loop Joins） 嵌套循环连接适合处理小量数据。Oracle 首先选择一张表作为连接的驱动表 （Driving Table），这张表也被叫做外部表（Outer Tabl...
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Because of how nested loop joins work, the second leg (there are four nodes) is executed per outer table record.
因为嵌套循环联接的工作方式，所以每隔一个外部表记录执行第二步(共4个节点)。
As previously stated, ordered input is essential to a merge scan join, but it is not required for nested loop joins.
如前所述，按顺序的输入对于合并扫描联接是必不可少的，但其无需嵌套循环联接。
However, the benefit of the merge scan join is that the inner table does not have to be scanned repeatedly as it does for nested loop joins.
然而，合并扫描联接的好处是不必反复地扫描内部表因为其为嵌套循环联接工作。
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