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分类： Oracle
2019-10-28 16:19:47
choose two
Examine this business rule:
Each studert can work on mutiple projects and eath project can have multiple students
You must desion an Entity Relationsep (ER) model for optional data storage and allow generating reports in this format:
STUDENT_ID FIRST_NAME LAST_NAME PROJECT_ID PROJECT_NAME PROJECT_TASK
Which two statements are true?
A) An associative table must be created with a composite key of STUDENT_ID and PROJECT_ID,which is the foreign key linked to the STUDENTS and PROJECTS entities.
B) The ER must have a many-to-many relationship between the STUDENTS and PROJECTS entities that must be resolved into 1-to-many relationships.
C) PROJECT_ID must be the primary key in the PROJECTS eitity and foreign key in the STUDENTS entity.
D) The ER must have a 1-to-many relationship between the STUDENTS and PROJECTS entities.
E) STUDENT_ID must be the primary key in the STUDENTS entity and foreign key in the PROJECTS entity.
Anaswer：AB
(解析：这道题涉及到调优问题，应用中经常出现多对多之间的关系，如何解决 STUDENTS and PROJECTS 两张表的多对多关系，可以创建一个中间表，这个表包含那两张表的主键列，同时是另外两张表的外键约束。通常这个表建成索引组织表。)
