Web-DSS-Chapter-03

More documents

Recommendations

Info

50 CHAPTER 3 ■ Entity-Relationship Modeling Rating MUSICIAN Performs COMPOSITION VENUE (a) ARTIST a1 a2 a3 a4 a5 a6 CONCERT c1 c2 c3 c4 c5 c6 c7 Performs r1 r2 r3 r4 r5 COMPOSITION m1 m2 m3 m4 m5 m6 (b) Figure 3.16 Examples of ternary relationships. (continues)
SECTION 3110 ■ Attributes of Relationships 51 Date STUDENT Uses EQUIPMENT PROJECT (c) STUDENT r1 r2 r3 r4 r5 PROJECT p1 p2 p3 Uses r1 r2 r3 r4 EQUIPMENT e1 e2 e3 e4 e5 (d) Figure 3.16 (continued) 3.11 Attributes of Relationships We have already discussed examples of E-R diagrams that reveal attributes stemming off relationships. Recall Figure 3.15(c), for example. In that E-R diagram, the attribute DateofOrder collects data for the relationship CUSTOMER places ORDER. Attributes on relationships are like attributes on entity types we have seen so far. An attribute on a relationship stores information related to the relationship. In Figure 3.17, the attribute Quantity stores the number of components that make up an entity type ITEM. Note that the attribute Quantity stems from the relationship and not from the entity.
Page 1 and 2: three Entity-Relationship Modeling
Page 3 and 4: SECTION 3.3 ■ Entity 35 Sends SUP
Page 5 and 6: SECTION 3.4 ■ Attributes 37 E-R d
Page 7 and 8: SECTION 3.5 ■ Relationships 39 St
Page 9 and 10: SECTION 3.7 ■ Cardinality of a Re
Page 11 and 12: SECTION 3.7 ■ Cardinality of a Re
Page 13 and 14: SECTION 3.8 ■ Unary Relationship
Page 15 and 16: SECTION 3.9 ■ Binary Relationship
Page 17: SECTION 3.10 ■ Ternary Relationsh
Page 21 and 22: SECTION 3.12 ■ Associative Entiti
Page 23 and 24: SECTION 3.14 ■ Enhanced Entity-Re
Page 25 and 26: SECTION 3.15 ■ Superclass, Subcla
Page 27 and 28: SECTION 3.15 ■ Superclass, Subcla
Page 29 and 30: SECTION 3.16 ■ Generalization and
Page 31 and 32: SECTION 3.17 ■ Participation and
Page 33 and 34: SECTION 3.17 ■ Participation and
Page 35 and 36: SECTION 3.18 ■ Superclass./Subcla
Page 37 and 38: SECTION 3.21 ■ Summary 69 3.20 In
Page 39 and 40: SECTION 3.22 ■ Exercises 71 12. U
Page 41 and 42: SECTION 3.22 ■ Exercises 73 7.
Page 43 and 44: SECTION 3.22 ■ Exercises 75 curre
Page 45 and 46: SECTION 3.22 ■ Exercises 77 below
Page 47 and 48: SECTION 3.22 ■ Exercises 79 c. Fo
Page 49 and 50: SECTION 3.22 ■ Exercises 81 attri

Web-DSS-Chapter-03

Create successful ePaper yourself

Delete template?

Save as template?