Join cardinality的意思|示意
加入基数
Join cardinality的网络常见释义
连接基数 l 连接基数（Join cardinality）：就是两个行集在连接之后产生的行数。连接就是由两 个行集产生的笛卡尔积，再由连接谓词过滤结果。
Join cardinality相关例句
Therefore, the join cardinality is the product of the cardinalities of two row sets, multiplied by the selectivity of the join predicate.
因此， 连接行集数是两个行集的行集数的乘积，被选择的谓词连接的乘积。
Cardinality affects join orders and join methods to a large extent.
这个基数会大大影响连接顺序和连接方法。
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.
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。
Notice that there is a significant difference between the cardinality shown in the fetch node on the outer side of the join in Figure 7.
请注意在图7中联接的外部Fetch节点上所显示的基数之间有一个显著的不同。
These expressions prevent the optimizer from assigning valid cardinality or selectivity estimates and can in turn affect the overall plan and the join method.
上面表达式使优化器不能有效分配基数或选择性消耗，可能会反过来影响整个执行计划。