Consider an ER diagram with entities Employee(emp_id, name), Project(proj_id, title), and a many-to-many relationship WorksOn between them. How should you map this relationship into tables?

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SQL - Table Relationships

Consider an ER diagram with entities Employee(emp_id, name), Project(proj_id, title), and a many-to-many relationship WorksOn between them. How should you map this relationship into tables?

AAdd proj_id as a foreign key column in Employee table

BAdd emp_id as a foreign key column in Project table

CCreate a new table WorksOn with columns emp_id and proj_id as foreign keys

DMerge Employee and Project tables into one

Step-by-Step Solution

Solution:

Step 1: Understand many-to-many relationships
Many-to-many means multiple employees can work on multiple projects and vice versa.
Step 2: Map many-to-many to tables
This requires a new table (junction table) that holds foreign keys from both Employee and Project tables.
Final Answer:
Create a new table WorksOn with columns emp_id and proj_id as foreign keys -> Option C
Quick Check:
Many-to-many = junction table with two foreign keys [OK]

Quick Trick: Many-to-many needs a new table with two foreign keys [OK]

Common Mistakes:

MISTAKES

Adding foreign key to only one table
Merging unrelated tables
Ignoring the need for a junction table

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Consider an ER diagram with entities Employee(emp_id, name), Project(proj_id, title), and a many-to-many relationship WorksOn between them. How should you map this relationship into tables?

Step 1: Understand many-to-many relationships

Step 2: Map many-to-many to tables

Final Answer:

Quick Check:

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