In this regard, the query is similar to a left outer join in SQL.
从这种意义上说，查询与 SQL中的左外连接相似。
Figure 8 shows that the left outer join operations are cascaded if a rule USES more than one reference column.
图8展示了如果规则使用了多个参考列，那么左外部连接就进行级联。
The combined record is much easier to use-you only have to check the PICTURE field to see if it's not null (which was the result of the LEFT OUTER JOIN).
而组合的记录使用起来要容易得多—只需检查PICTURE字段，查看它是否为空(这是LEFT OUTER JOIN的结果)。
The following illustration shows a conceptual view of two sets and the elements within those sets that are included in either an inner join or a left outer join.
下面的概念图显示了两个集合中的完整项目，以及这两个集合彼此进行内部联结或左外部联结之后剩下的项目。
A left outer join is a join in which each element of the first collection is returned, regardless of whether it has any correlated elements in the second collection.
左外部联接是这样一个联接：在其中返回第一个集合的每个元素，而无论该元素在第二个集合中是否具有相关元素。
When you select an option to create an outer join, the diamond graphic in the join line changes to indicate that the join is a left outer, right outer, or full outer join.
当选择创建外部联接的选项时，联接线中的菱形图会改变，以指示联接是左外部联接、右外部联接还是完全外部联接。
Outer join in which all rows from the table represented on the left will be included, even if they do not have matches in the related table.
外部联结，将包括右边资料表的所有资料列，即使该资料列在相关资料表中并没有相符项目。
Outer join in which all rows from the table represented on the left will be included, even if they do not have matches in the related table.
外部联结，将包括右边资料表的所有资料列，即使该资料列在相关资料表中并没有相符项目。
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