Eng.Samir Sabry
IT Instructor
Mapping Rules
Step 1: regular entity types
Create a new relation that includes Simple attrib...
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Mapping rules

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Mapping rules

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Mapping rules

  1. 1. Eng.Samir Sabry IT Instructor Mapping Rules Step 1: regular entity types Create a new relation that includes Simple attributes  For a composite attribute include only the simple component attributes  Leave out multivalued attributes (to step 6)  Pick a PK Step 2: weak entity types Note: Weak entity type has no key - Related to an identifying or owner entity type. Has total participation constraint with identifying entity.  Create a new relation with simple attributes  Include an FK to the owner entity's relation Step 3: 1:1 relationship types Add to one of the participating relations an FK to the other relation:  It is better to add to a relation that has total participation in the relationship  Include any relationship attributes Step 4: 1: N relationship types  Add to the relation on the N-side an FK to the other relation.  Include any relation attributes Step 5: M: N relationship types  Create a New relation containing as FK of the primary keys of both entity types participating relations  Include any relation attributes Step 6: multi-valued attribute Create new relation containing FK of the PK from the Entity Step 7: ternary relationship types  Create new relation containing a FK referencing each of the 3 entities involved  Include any relation attributes Notes: How many relations? 1. Entity (both regular and weak) 2. M:N relationship 3. Multi-valued attribute 4. Ternary relationship

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