May 16, 2012 · Could somebody explain to me, with the help of examples, what is cardinality in databases?

Sep 6, 2023 · On one server, most of the queries which are executed by a 3rd party application, are listed with "Downlevel CE" (Legacy Cardinality Estimator in use).

对于数据库而言，索引应该尽量选择高选择性的，所以必须重视 Cardinality （基数）值。 Cardinality 指的是一个列中不同值的个数。 最大索引意味着某个列的每个值都是唯一的，比如 …

Please remove the column or increase the 'cardinality_threshold' parameter. Increasing the cardinality_threshold may produce long processing times r asked Apr 30, 2020 at 13:49 …

Jun 24, 2025 · SQL Server query optimizer, being 'cost-based', fundamentally relies on cardinality estimation, using per-attribute summary statistics (histograms) to generate efficient execution …

本回答只讨论实数集 \mathbb R 中的勒贝格测度。从几何的角度来看， 对实数集 \mathbb R 中的一些子集定义测度，就是为它们定义长度。从概率的角度来看， 确定区间 [0,1] 的某个子集的 …

Aug 28, 2014 · High-cardinality - many tuples, low-cardinality - few tuples. While the Wikipedia article on Cardinality (SQL statements), defines it as follows: Cardinality refers to the …

Mar 6, 2020 · Microsoft introduced the new Cardinality Estimator in the SQL Server engine in 2014. If the database was set to an older compatibility mode, it was still using the old …

基数估算（Cardinality Estimation），也称为 count-distinct problem，一直是大数据领域的重要问题之一。 顾名思义，基数估算就是为了估算在一批数据中，它的不重复元素有多少个。

Please look at this query plan If cardinality estimate was affected by the conversion, then estimated number of rows would be significantly different than actual number of rows, but they …