in ERD of a system in which teachers evaluating other teachers of their departments how can i connect Teacher, evaluation_result entiy,

Question

A teacher could be an evaluator and also be an evaluatee. How can I achieve this?

Answer 1

You would just add another foreign key to Eval_Result to link to the Evaluatee

So you would have:

Teacher

• T_ID - primary key
• Teacher info - other fields

Eval_Result

• Eval_ID - primary key
• Evaluator_ID - teacher that did the evaluation - foreign key to Teacher
• Evaluatee_ID - teacher being evaluated - foreign key to Teacher
• Results - other fields

Answer 2

Teacher as evaluator can evaluate multiple Teachers (evaluatees). This is a one-to-many self-referencing relationship.

Evaluator -|--< Evaluatee

Teacher:

id [Primary Key]
name
evaluator [Foreign Key referencing Teacher's id]
evaluation result id [Foreign Key referencing Evaluation Result's id]

Evaluation Result:

id [Primary Key]
result details

A Teacher (evaluatee) can have one evaluation result.

Teacher (evaluatee) -|--|- Evaluation Result