关系代数笛卡尔积

Question

我开始学习数据库，现在我只学习关系代数并遇到问题。如下表所示：

R1 = {(Jon, Smith, 24, British, Single, UK, Guitarist),
(Jon, Maynard, Smith, 74, British, Widowed, UK, Scientist),
(Jon, Travolta, 50, American, Married, USA, Plumber),
(Katy, Pierce, 23, UK, Single, Caiman Island, unknown)}
With Schema = {Name, Surname, Age, Nationality, Status, Country, Job}

如何使用自笛卡尔/交叉运算计算R4 = R1 X R1？

Answer 1

尝试SELECT * FROM R1 CROSS JOIN R1 tab2

electron-builder

Answer 2

只需从没有连接的两个表中选择

Select r1.*,r2.* From r1,r1 r2