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Mapping Unary 1:1 and 1:M Relationships,”A unary 1:1 or 1:M relationship requires using an entity’s primary key as a foreign key within the relational schema. Ex.MECHANIC(MechID, Salary
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Read moreMapping Unary M:N Relationships,”Mapping this relationship requires adding an intersection relation:MECHANIC(MechID, Salary)SUPERVISES(SupervisorID, SuperviseeID)In this case
Average Rating 0 out of 5 stars. 0 votes.You must log in to submit a review.Mapping Unary M:N Relationships,”Mapping this[…]
Read moreMapping Ternary Relationships,”STUDENT(StudentID, StudentName)COURSE(CourseID, CourseName)PROFESSOR(ProfID, ProfName)RELATESTO(StudentID, CourseID
Average Rating 0 out of 5 stars. 0 votes.You must log in to submit a review.Mapping Ternary Relationships,”STUDENT(StudentID, StudentName)COURSE(CourseID, CourseName)PROFESSOR(ProfID,[…]
Read moreMapping Weak Entities,”except the primary key(s) from any attached strong entity or entities must be included with the weak entityMOVIE(MovieID, MovieName, ReleaseDate)VIDEO-TAPE(CopyNumber, DateAcquired
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Read moreMapping Aggregation,”Relationships involving aggregations should reference all necessary primary keys from inside the aggregationEx.STUDENT(StudentID, StudentName)COURSE(CourseID, CourseName)PROFESSOR(ProfID, ProfName)TAKES(StudentID, CourseID)TEACHES(ProfID, StudentID
Average Rating 0 out of 5 stars. 0 votes.You must log in to submit a review.Mapping Aggregation,”Relationships involving aggregations should[…]
Read moreMapping Specialization/Generalization,”SUPERTYPE(CommonIdent, CommonAttr1, CommonAttr2)SUBTYPE1(CommonIdent, UniqueAttr1)SUBTYPE2(CommonIdent, UniqueAttr2, UniqueAttr3)As an alternative mapping for total specialization with disjoint relations, you can may consider dropping the supertype and creating tables for each subtype:SUBTYPE1(CommonIdent, CommonAttr1, CommonAttr2, UniqueAttr1)SUBTYPE2(CommonIdent, CommonAttr1, CommonAttr2, UniqueAttr2, UniqueAttr3)SUBTYPE3(CommonIdent, CommonAttr1, CommonAttr2
Average Rating 0 out of 5 stars. 0 votes.You must log in to submit a review.Mapping Specialization/Generalization,”SUPERTYPE(CommonIdent, CommonAttr1, CommonAttr2)SUBTYPE1(CommonIdent, UniqueAttr1)SUBTYPE2(CommonIdent,[…]
Read moret/f? minimum cardinality influences relational schemas
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Read moreMiscellaneous issues 1,”For composite attributes, include only the atomic attributes:CUSTOMER(CustID, Age, Street, City, State, Zip)For a composite attribute that serves as a primary key, you would need to underline all sub-attributes in the relation to clarify this (e.g., for a composite primary key such as FullName, this may break down into: FirstName, MiddleName
Average Rating 0 out of 5 stars. 0 votes.You must log in to submit a review.Miscellaneous issues 1,”For composite attributes,[…]
Read moreMiscellaneous issues 2,”For multi-valued attributes, avoid repeating groups (e.g., columns such as Address1, Address2, and Address3) by creating a separate table/schema as you would for M:N relationships:STUDENT(StudentID)STUDENTADDRESS(Address
Average Rating 0 out of 5 stars. 0 votes.You must log in to submit a review.Miscellaneous issues 2,”For multi-valued attributes,[…]
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