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NLJOIN

网络循环连接；嵌套循环联接

NLJOIN

NLJOIN

NLJOIN

循环连接

...行这种递归查询的。嵌套的循环连接（NLJOIN）以一个临时结果表（TEMP）为基础，而这次连接的的结果又再次通过 UNIO…

嵌套循环联接

图 6a. 嵌套循环联接 (NLJOIN) 的访问路径图返回文章打印此页面帮助联系编辑提交内容网站导航订阅源在线浏览每周时事 …

2

As such, the NLJOIN does not act as a classical join with two input legs, but facilitates access to the XML data for the XSCAN operator .

同样地，NLJOIN 并没有充当拥有两个输入的标准连接，而是协助 XSCAN 操作符来访问 XML 数据。

3

Similarly , the last leg in the access path graph is evaluated eight times , once for each record produced by the first NLJOIN node .

同样，访问路径图的最后一步要评估 8 次，通过第一个 NLJOIN 节点产生的每条记录都要评估一次。

4

These eight qualifying records are then taken as the first input to the NLJOIN node immediately above the FETCH node.

然后用作第一个联接操作的这 8 条合格的记录将立即输入到在 FETCH 节点之上的 NLJOIN 节点。

6

Since the OUTER of this NLJOIN, TBSCAN(2 ), is applying local predicates, you must also add the predicates to the count query .

因为该 NLJOIN 的 OUTER 即 TBSCAN （2 ）应用于局部断言，必须将该断言增加到计数查询。

7

The NLJOIN node will eventually produce eight joined records as the output (Output Cardinality value is 8 ).

NLJOIN 节点将最终产生 8 条已联接的记录作为输出（输出基数值是 8 ）。

8

For each row , the nested loop join (NLJOIN) operator passes a pointer to the corresponding XML document to the XSCAN operator .

对于每一行，嵌套循环连接（NLJOIN ）操作符把指向相应的 XML 文档的指针传递给 XSCAN 操作符。

9

Thus the estimation for final the result set is one row only (NLJOIN(2 )), which matches the real result .

因此结果集中最终的评估值只有一个（NLJOIN （2 ）），这是符合实际结果的。

10

You can generate NLJOIN(5 ) and NLJOIN(4 ) yourself as an exercise to compare with these last two cases above .

作为练习，可以自己生成 NLJOIN （5 ）和 NLJOIN （4 ）的查询，并与上面最后两个查询进行比较。

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