英文: 1 Base cardinality is the number of rows in a base table. 中文: 基本的行集数是一个表的行数。 更详细... 英文: 3 Join cardinality is the number of rows produced when two row sets are joined together. 中文: 连接行集数是两个行集被连
caridnality的解释是Cardinality represents the number of rows in a row set.字面上的意思是代表行集中的行数
The number of rows in the table (cardinality). 表中的行数(基数)。 The table cardinality for CUST_CUSTOMER is about 30000. CUST_CUSTOMER的表基数大约是30000。 Changing cardinality of existing output data structures. 变更现有输出数据结构的基数性。 This is close, but higher than the real car...
美 英[kɑːdɪ'nælɪtɪ] n.〔数〕基数 网络基数性;势;基数或势 英汉 网络释义 n. 1. 〔数〕基数 释义: 全部,〔数〕基数,基数性,势,基数或势
用法例句 1. Ncardinality(account, address). n关系(帐户、地址)。 2. Dealing with HL7cardinalityand optionality. 处理HL7基数和可选性。 3. The number of rows in the table (cardinality). 表中的行数(基数)。 4. The tablecardinalityfor CUST_CUSTOMER is about 30000. ...
Relationships exist between two query subjects or between tables within a query subject. The cardinality of a relationship is the number of related rows for each of the two objects in the relationship. The rows are related by the expression of the relati
(and sometimes only) column in an index. This is due to the fact that the index will only request a small number of rows from the table. Low cardinality columns are more difficult to index correctly. For example, consider the following query: select * from employee where sex='F'; ...
如下所示,Esimated Number of Rows的取值就来源于AVG_RANGE_ROWS . 因为11222位于11185 与 11223之间。所以取RANGE_HI_KEY=11223这条记录对应的AVG_RANGE_ROWS(4.32432)。 3: 如果在查询条件中使用变量(编译时未知特定搜索值),则预估行数(Esimated Number of Rows)= 密度* 采样的行数: ...
Cardinality: In set theory, it is the number of elements in a set. In databases, it will be the number of rows in a table or after applying a predicate. Selectivity: Fraction of records returned after applying a predicate. For example, a table containing people and about one third of th...
where sex='F'; Without an index, this query will perform a full table scan. >This seem undesirable. However, adding an index will reduce the number of rows retrieved by the table, but may actually take much longer due to the index usage. In this case, a normal b-tree index is proba...