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ER model

ER-model : Attributes: simple attribute - atomic values, which cannot be divided further. For example, student's phone number, course ID etc. Composite attribute - made of more than one simple attributes. For example, a student's complete name may have first_name and last_name. Derived attribute - their values are derived from other attributes present in the database. For example, age can be derived from a person's birthday. Single-value attribute - attributes that contain single value. For example - course ID. Multi-value attribute - attributes that contain more single value. For example - a person's phone number. You may have more than one phone number, right? A data can belongs to more than one attributes which is mentioned above can. For example, phone number is a simple attribute. It can also be multi-value attribute. In this case, we say that it is a simple multi-valued attribute. Relationship: One-to-one: One entity from entity set A can be associated with at most one entity of entity set B For example, you are in one of the class in your school. One-to-many − One entity from entity set A can be associated with more than one entities of entity set B however an entity from entity set B, can be associated with at most one entity. For example, a teacher teaches more than one class. Many-to-one − More than one entities from entity set A can be associated with at most one entity of entity set B, however an entity from entity set B can be associated with more than one entity from entity set A. For example, all the teacher who teach the same subject are in the same office. Many-to-many − One entity from A can be associated with more than one entity from B. For example, every student can take more than one course and the course can be taken by many students. Entity : A thing in the real world with an independent existence. For example, students in your school. This picture can help you draw the type of each attributes and relationship. https://i.imgur.com/ywy0lgi.png reference: https://www.tutorialspoint.com/dbms/er_diagram_representation.htm My English is really poor. If there is any mistake about the grammar, please accept my apology.


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B1

我…我看到了什麼東西qq

原 Po 回覆:

大學生準備期中考😂 所以把重點整理出來 po出來是想說 如果有一天有人學到 可以拿來用 之後再發應該是演算法的東西了吧🤔 我好感動有人看到這篇文章😭

1
B2

抱持著尊敬的心情來留言(*´∇`*) 真的很喜歡程式設計之類的東西,但是我的腦子真的學不起來qq所以就沒有走這條路哈哈哈

原 Po 回覆:

哈哈我會走這條路 只是它比較適合我而已😂 如果有機會還是可以再嘗試看看啦😊 如果可以 希望可以繼續關注之後的文😭 雖然本來就不太可能有人會看 但是我還是希望有人看到啊😭

1
B3

可以阿!只是我看不懂而已哈哈哈

原 Po 回覆:

如果是中文的會比較有幫助嗎XD 雖然我不太擅長把它翻成中文

0
B4

欸勒那我要怎麼關注你勒 是匿名欸qq

原 Po 回覆:

我也不知道有什麼方法XD

0
B5

欸豆,你會用站內信嗎(我是不會啦哈哈哈 翻成中文當然會好一點阿,但是一些專有名詞我還4看不懂(•ω•)

0
B6

可以請教妳嗎ε≡≡ヘ( ´Д`)ノ

原 Po 回覆:

可以啊😂 如果有需要的話 可以問😊 我也是因為希望有人可以更方便的學 才發文的😂

0
匿名
B7

哇 是ER圖

原 Po 回覆:

如果有錯 歡迎指正😂

0
匿名
B8

我這學期也有修資料庫欸 可是你都寫英文 我放棄閱讀…xd

原 Po 回覆:

抱歉😅 上課的投影片都是這樣寫的 所以就習慣這樣用了 我有想過下一次要不要發中文的文😂

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ER model

ER-model : Attributes: simple attribute - atomic values, which cannot be divided further. For example, student's phone number, course ID etc. Composite attribute - made of more than one simple attributes. For example, a student's complete name may have first_name and last_name. Derived attribute - their values are derived from other attributes present in the database. For example, age can be derived from a person's birthday. Single-value attribute - attributes that contain single value. For example - course ID. Multi-value attribute - attributes that contain more single value. For example - a person's phone number. You may have more than one phone number, right? A data can belongs to more than one attributes which is mentioned above can. For example, phone number is a simple attribute. It can also be multi-value attribute. In this case, we say that it is a simple multi-valued attribute. Relationship: One-to-one: One entity from entity set A can be associated with at most one entity of entity set B For example, you are in one of the class in your school. One-to-many − One entity from entity set A can be associated with more than one entities of entity set B however an entity from entity set B, can be associated with at most one entity. For example, a teacher teaches more than one class. Many-to-one − More than one entities from entity set A can be associated with at most one entity of entity set B, however an entity from entity set B can be associated with more than one entity from entity set A. For example, all the teacher who teach the same subject are in the same office. Many-to-many − One entity from A can be associated with more than one entity from B. For example, every student can take more than one course and the course can be taken by many students. Entity : A thing in the real world with an independent existence. For example, students in your school. This picture can help you draw the type of each attributes and relationship. https://i.imgur.com/ywy0lgi.png reference: https://www.tutorialspoint.com/dbms/er_diagram_representation.htm My English is really poor. If there is any mistake about the grammar, please accept my apology.

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