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实例 求学生关系 S 和选课关系 S C 的 θ 联结 S ⋈ SC

实例 求学生关系 S 和选课关系 S C 的 θ 联结 S ⋈ SC. s.sno<sc.sno. S. SNO SNAME SEX BIRTHDAY. SC. SNO CNO. 1001 c001 1001 c003 1002 c001 1003 c001 2001 c001 2001 c003. 1001 黄鹏 男 1981-10-12 1002 张寅秋 女 1998-06-12 赵程 男 1986-08-26

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实例 求学生关系 S 和选课关系 S C 的 θ 联结 S ⋈ SC

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  1. 实例 求学生关系S和选课关系SC的θ联结S⋈ SC s.sno<sc.sno S SNO SNAME SEX BIRTHDAY SC SNO CNO 1001 c001 1001 c003 1002 c001 1003 c001 2001 c001 2001 c003 • 1001 黄鹏 男 1981-10-12 • 1002 张寅秋 女 1998-06-12 • 赵程 男 1986-08-26 • 张宇蛟 男 1989-11-06 • 庄烨炜 男 1989-02-16 S. SC. θ联结 SNO SNAME SEX BIRTHDAY SNO CNO 1001 黄鹏 男 1981-10-12 1003 c001 1001 黄鹏 男 1981-10-12 1002 c001 1001 黄鹏 男 1981-10-12 2001 c001 1001 黄鹏 男 1981-10-12 2001 c003 1002 张寅秋 女 1998-06-12 1003 c001 1002 张寅秋 女 1998-06-12 2001 c001 1002 张寅秋 女 1998-06-12 2001 c003 1003 赵程 男 1986-08-26 2001 c001 1003 赵程 男 1986-08-26 2001 c003

  2. 实例 求学生关系S和选课关系SC的等值联结S⋈ SC s.sno=sc.sno S SNO SNAME SEX BIRTHDAY SC SNO CNO 1001 c001 1001 c003 1002 c001 1003 c001 2001 c001 2001 c003 • 1001 黄鹏 男 1981-10-12 • 1002 张寅秋 女 1998-06-12 • 赵程 男 1986-08-26 • 张宇蛟 男 1989-11-06 • 庄烨炜 男 1989-02-16 等值联结 S.SNO SNAME SEX BIRTHDAY SC.SNO CNO 1001 黄鹏 男 1981-10-12 1001 c001 1001 黄鹏 男 1981-10-12 1001 c003 1002 张寅秋 女 1998-06-12 1002 c001 1003 赵程 男 1986-08-26 1003 c001 2001 张宇蛟 男 1989-11-06 2001 c001 2001 张宇蛟 男 1989-11-06 2001 c003

  3. 实例 求学生关系S和选课关系SC的自然联结 S⋈ SC S SNO SNAME SEX BIRTHDAY SC SNO CNO 1001 c001 1001 c003 1002 c001 1003 c001 2001 c001 2001 c003 • 1001 黄鹏 男 1981-10-12 • 1002 张寅秋 女 1998-06-12 • 赵程 男 1986-08-26 • 张宇蛟 男 1989-11-06 • 庄烨炜 男 1989-02-16 自然联结： ，联结条件为同名字段相等 字段为S表字段加SC表的新字段 自然联结 SNO SNAME SEX BIRTHDAY CNO 1001 黄鹏 男 1981-10-12 c001 1001 黄鹏 男 1981-10-12 c003 1002 张寅秋 女 1998-06-12 c001 1003 赵程 男 1986-08-26 c001 2001 张宇蛟 男 1989-11-06 c001 2001 张宇蛟 男 1989-11-06 c003

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