الاخوة الاعزاء:

ارغب في بعض الامثة الواقعية للعلاقات One-One & One-Many& Many-Many

وشكراً للتعاون البناء.

Dear .. I hope this will answer you in good way >>

- There are three types of relationships:

A) One-to-One (1:1)
B() One-to-Many (1:N)
C() Many-to-Many (M:N)

- What is a Relationship?

Definition in class: An association between 2 (or more) separate entities.

In a one-to-one relationship, each record in Table A can have only one

matching record in Table B and each record in Table B can have only

one matching record in Table A. This type of relationship is NOT

common, because most information related in this way would be in one

table. You might use a one-to-one relationship to divide a table with too

many fields, to isolate part of a table for security reasons, or to store

information that applies only to a subset of the main table. For example,

you might want to create a table to track employees participating in a

fundraising soccer game.

Other Example: Relation between General Manager & Human Resource

Manager in any Company is mostly One to One Relation.

Many-to-many Relationship

In a many-to-many relationship, a record in Table A can have many

matching records in Table B, and a record in Table B can have many

matching records in Table A. This type of relationship is only possible

by defining a third table, called a junction table, whose primary key

consists of two fields: the primary keys from both Tables A and B. A

many-to-many relationship is actually two : one-to-many relationships

with a third table. For example, the Orders table and the Products table

In this case we have a many-to-many relationship that's defined by

creating two :one-to-many relationships with the Order Details table.

السلام عليكم ورحمة الله وبركاته

مرفق ملف يوضح العلاقات والترابط بينها

وهو عبارة عن ملخص لبعض فصول الكتاب العربي الموجود في منتدى المبتدئين

الكتاب الثاني : تصميم قواعد البيانات

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