??????????????????????????????? E-R Model ?????????????????????

1
??????????????????????????????? E-R Model
?????????????????????
E-R Model Entity Relationship
Model ??????????????????????? ????????
ERD (Entity Relationship Diagram)
2
?????????? E-R Model
- ????????????????????????????????????????????????
????????????????????? - ??????????????????????????
????????
3
Entity Relationship Model (E-R Model)

• ??? ?????????????????????????????????????????????
  ???????????????????????????
• ??????????????????????????????????????????
  ?????????? 2 ????
• ???????? (Entity)
• ???????????? (Relationship) ??????? Entity

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????????????????????????? E-R Diagram
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????????????????????????? E-R Diagram
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????????????????? E-R Diagram ?????? Chen Model

• Entity
• ??????????????????????????????????????????????????
  ????????????????????
• ????
• ????? (???????, ???????, ???????,
  ????????,??????)
• ??????? (???????, ?????, ???, ???????)
• ????? (??????, ?????, ???????????,??????)
• ????????? (???????, ????????????,
  ???????????,????,???)
• ???????????????????????????????????????? Entity
  ?????????

????????? Entity
???????
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???????? (Entity)

• ???????????????? ??????????????????????? ????
  ????? ????????? ???????
• ????????????????????
• ????????????????? (Property) ???????????????
  (Attribute) ??? ???? ????? ???? Attribute ????
  ??????? ???? ??? ???????????? ???

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???????? (Entity)

• ??????????? 3 ????
• Regular Entity ??? Entity ???? ? ?? ?????
  Attribute ????????????????????????????????? Tuple
  ???
• Weak Entity ???? Entity ?????? ??? Entity
  ???????????? Attribute ??? Entity
  ???????????????????????????????????????? Tuple
• Composite Entity ??? Entity ????????? Attribute
  ??????? Primary key ??? 2 Entity
  ???????????????????????????? Tuple ???? Entity
  ??????????????????????????????????????? MM
  ??????? ??? 1M

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Regular Entity
10
Weak Entity
11
????????? Strong Weak Entity
Student (Strong)
Subject (Strong)
???? ???? ???
45001 ???? ????????????
45002 ????? ?????
???????? ????????
01 ?????????
02 ?????????
Regis_Detail(Weak)
???? ?????????? ????????
45001 1/45 01
45002 1/45 01
45001 1/45 02
45002 1/45 02
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Composite Entity
13
Attribute ???? Property

• ???????????????? ? ??? Entity

Attribute
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• Attributes
• ?????????????????????????? Entity
• ???? Attributes ??? ??????? ??????????
• ?????????????
• ????-???????
• ???
• ?????????
• ????????? Attributes ?????????????????
  ???????????? Attributes ??????????????
  ????????????????????? Entity ?????? ????

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• ???????? Attributes

Sex
Name
Employee
Emp_ID
Salary
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Attributes

• Attributes ?????????????????? 6 ??????
• 1 Simple Attributes
• Attributes????????????????????????????????? ????
  ???,?????????
• 2 Composite Attributes
• ????????????????????? Simple ?????????????????????
  ??????? ???? ???????? ???????????????????????
  Attributes ???? ??? ????
• 3 Key Attributes
• ???? Attributes ??????????????????????????????
  Entity ??????? (??????????????)
• ????????? ER Diagram ?????????????? Attributes
  ??????? Key ????

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Attributes

• 4 Single - Valued Attributes
• Property ????????????????????????????????????
  ???? Attributes ??? ??????????????? ??? ???? ????
  ???????? ??????????????????????????
• ????????????????? ????????????????????????
• 5 Multi - Valued Attributes
• ????????????????????? Single ?????????????????????
  ???????????? ???? ????????????????????????????????
  ?????????????????????????
• ????????????????????????
• 6 Derived Attributes
• ???? Property ??????????????????? ?????????????
  Property ???? ? ???? ?????????? ???????????
  Property ???????
• ????????????????????????

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????????? Attribute ???? Property

• Simple Attribute

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????????? Attribute ???? Property

• Composite Attribute

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????????? Attribute ???? Property

• Key Attribute

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????????? Attribute ???? Property

• Single-Valued Attribute
• ??? Attribute ??????????????? Attribute ????
  ??????????????????? ???? ?????????? ???????

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• ??????????? Attributes ???????? ?

Composite
Name
Surname
Sex
Name_Surname
Birthday
Derived
Student
ID
Age
key
Tel
Multi - Valued
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???????????? (Relationship)

• ??????? Entity ?????????????????????????? 2
  Entity ??????
• ??????????????????????? Entity ????? Attributes
  ???????
• ??????????????????????????????????????????????????
  ????????????? (Diamond) ??????????????????????????
  ??????? ?
• ??????????????????????????????????????? Entity
  ???? ? ????

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???????????? (Relationship)

• ???????? Relationship

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????????? Relationship

• 1. One-to-One Relationship
• ?????????????????????????????? Entity
  ?????????????????? ?????????????? Entity
  ??????????? ???????????????????????

1
1
Car
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????????? Relationship

• 2. One-to-Many Relationship
• ?????????????????????????????? Entity
  ?????????????????? ?????????????? Entity
  ??????????? ??????? 1 ??????

1
M
Car
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????????? Relationship

• 3. Many-to-Many Relationship
• ???????????????????????????????? 1 ?????? ?????
  Entity ?????????????????? ?????????????? Entity
  ??????????? ??????? 1 ??????

M
N
Account
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Relationship ???? Connectivity ??? One to One ,
11
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Relationship ???? Connectivity ??? One to Many,
1M
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Relationship ???? Connectivity ??? Many to
Many, MN
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?????????? E-R diagram ???? Table

• Strong Entity

????? Student
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?????????? E-R diagram ???? Table

• Entity ????? Composite Attribute

????? Student
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?????????? E-R diagram ???? Table

• Entity ????? Multi-value Attribute

???????????? Tel ??? 1 ?????
????? Student
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?????????? E-R diagram ???? Table

• Weak Entity

????? Timestamp
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?????????? E-R diagram ???? Table
?????????????????

• ???????????????????????????? (One to One, 11)

??????
?????????? ?????????? ??????? ??????????

?????????? ?????????? ???????

??????
????
?????????? ??????????

??????
?????????? ?????????? ??????????

??????
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?????????? E-R diagram ???? Table
?????????????????

• ???????????????????????????? (One to Many, 1M)

??????
?????????? ?????????? ??????? ??????????

??????
?????????? ??????????

37
?????????? E-R diagram ???? Table
?????????????????

• ???????????????????????????? (Many to Many, MN)

???????????? ?????????? ?????????

??????????
?????????? ?????????? ????

???????????? ??????????

??????????
??????
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???????????????????????? MM ?????? 1M
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?????????????????????? E-R Model

• 1. ?????????????????????????????????????????
• ?????????????????????
• ?????????????????????
• ???????????????
• ?????????????????

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• 2. ????? Entity ???????????????????????
• ??????????????????????????????????????????????????
  ? ?????????????????????????? Entity
• ??????????????????? ? ???????????? Entity
  ???????????? ?????????????????????????????????????
  ???????????????????
• ??????????? Entity ?????????????? Entity
  ??????????????????????????????

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• 3. ??????????????????????????? Entity
• ???????? Entity ????????????????????????
  ??????????????????????????? ??????????????????????
  ????????
• One to One Relationship
• One to Many Relationship
• Many to Many Relationship

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• 4. ???????????????????? Entity
• ????????????????????? (Attributes) ?????? Entity
  ???????????????????? Attributes ?????
• ??????????????????????? Attributes
  ???????????????
• Composite Attributes
• Derived Attributes

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• 5. ???????? Primary Key ???????? Entity
• ??????????????? Entity ????? Entity
  ??????????????????????????????????????????????????
  
• ????????????????? Primary Key ???????

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?????????????????????????????? E-R Model

• Ex
• ??????????????????????????????????? 3 ??? ???
  ?????, ???????????, ???????????
• ??????????????????????????????????????? ?
• ??????????????????????????????????????? ? ??
• ???????????????????????????? ?????????????????????
  ?????????????????
• ?????????????????????????????????????????

45

• ????? Entity ???????????????????????
• Entity Faculty ????????????????????
• Entity Department ?????????????????????
• Entity Teacher ????????????????????????
• Entity Subject ?????????????????????

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• ???????????????????????? Entity

1
M
1
M
1
M
47
1
M
M
M
1
1
48

• ????????????????? Entity
• Faculty
• Department

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• Teacher
• Subject

50

• ???????? Primary Key ??? Entity
• Entity Faculty ??? Faculty_ID
• Entity Department ??? Dep_ID
• Entity Teacher ??? Teacher_ID
• Entity Subject ??? Subject_ID

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(No Transcript)
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?????????????????????????????? E-R Model

• Ex ???????? ER-Diagram ???????????????????
  ????ABC ???????????
• ??????
• ????????????????????????????????????????????
• ???????????????????????????????????????
• ???????????????????????????????????????????????
• ???????????????????????

53

• ????? Entity ???????????????????????
• Entity Customer ???????????????????????
• Entity Employee ???????????????????????????
• Entity Product ???????????????????????
• Entity TypeProduct ???????????????????
• Entity Bill ????????????????????????

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• ???????????????????????? Entity

??
1
M
Employee
Bill
??
1
M
TypeProduct
Product
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??
M
M
Bill
Product
Bill_detail
M
1
1
M
Bill
Product
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• ????????????????? Entity

Emp_ID
Product_ID
Employee
Emp_name
Product
Product_name
salary
price
TypeProduct
TypeName
TypeID
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Cus_ID
Bill_No
Customer
Cus_name
Bill
Bill_date
Address
Emp_ID
58
ER-Diagram ???????????????????
Product_ID
Product_name
Product_ID
Price_s
Detail_ID
Bill_No
price
Bill_detail
Bill_detail
1
1
M
M
Bill
Product
Bill_date
M
M
Amount
M
Emp_ID
??
Bill_No
??????
TypeName
1
??
TypeID
TypeProduct
1
1
Employee
Emp_name
salary
Emp_ID