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SQL - Multiple one-to-many relationships

开发者 https://www.devze.com 2023-01-10 11:00 出处:网络
Is it possible somehow to do multiple one-to-many relationships between 2 tables? Like: Table abc abcID defID

Is it possible somehow to do multiple one-to-many relationships between 2 tables? Like:

Table abc

  • abcID
  • defID
  • message

Table def

  • defID
  • abcID
  • message

If yes how c开发者_Python百科an I then make a new abc entry with the entity framework?


You only need a single Many-Many relationship. Simply move QuestionId out of the quiz_answers table and move AnswerId out of the quiz_questions table:

Create Table quiz_questions
(
QuestionId ... Not Null Primary Key
, Question ...
, ...
)

Create Table quiz_answers
(
AnswerId ... Not Null Primary Key
, Answer ...
, ...
)

Create Table quiz_question_answers
(
QuestionId ... Not Null References quiz_questions ( QuestionId )
, AnswerId ... Not Null References quiz_answers ( AnswerId )
, Constraint PK_quiz_question_answers Primary Key ( QuestionId, AnswerId )
)


Yes, it is a one-to-one join from abc to def and then another from def back to abc; so abc joins to def on defID and def joins to abc on abcID.

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