联盟，笛卡尔积 [英] union,cartesian product

问题描述

使用您在上一个示例中创建的表来表示笛卡尔乘积，并集的特定示例，并将差异设置为日常英语和关系代数.
可以只具有一个关系(表)的联合或笛卡尔积吗?抱歉，我无法使该表格适合您的桌子，但该属性是许可证号，保质期，yeinsuredExpired，型号，颜色，自动/人，所有者

请有人帮忙，我仍在等待答案.可以在此表格上执行此操作吗?

express a specific example for cartesian product, union, and set difference as everyday English and as relational algebra using the table you created in the previous example.
Is it possible to have union or cartesian product with only one relation(table)? sorry for the table i cant make it fit, but the attributes are licenceNo, yrinsured,yeinsuredExpired,model,color,auto/man,owner

Please may someone help, I am still waiting for an answer. Can this be done to this table and how?

01  licenceNo    yr_insured    yr_insuredExpired    model    color    auto/man    owner
02  111-aaa                1999          2009             beatle    pink     auto     Johnson
03  222-bbb                1999          2009            mustang    white    auto     Trot
04  333-ccc                2000          2010            tacoma    blue      auto     White
05  444-ddd                2007          2017             f-350    blue      auto     Black
06  555-eee                2005          2015            d-2500    black     auto     Smith
07  666-fff                2007          2017           corolla    white     man      Lee
08  777-ggg                2010          2020            matrix    white     auto     Kim
09  888-hhh                2008          2018             civic    green     man      Singh
10  999-iii                2008          2018           escalde    black     auto     Williams
11  000-jjj                2009          2019              civic    red      auto     Vanderhoot

推荐答案

是的，是的，不是的. :)

例如，在包含经理属性的员工表中，发现层次结构的一种解决方案是使用自连接，这会导致笛卡尔积.

是的，因为只有一张桌子.否，因为出于连接目的将其视为两个表.

Well, yes and no. :)

For example in an employee table that includes a manager attribute, one solution to discovering the hierarchy is to use a self join which can result in a cartesian product.

So yes, because there would only be one table. No because it is being treated as two tables for the purposes of the join.

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