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Semester 1/Database Systems/Assignment/ER Diagram.md

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+Key Phrases:
+
+1. Transplant operations [are carried out at specialist transplant units. They] are never split across more than one unit.
+An operation takes place at 1 Unit.
+
+2. Each unit is based at one hospital only
+A unit can only be in 1 hospital
+
+3. Specialises in one type of transplantation
+A unit has 1 specialisation
+
+4. A unit can transplant the other types of organ which lie outside of its area of expertise.
+A unit does not specifically have to transplant it's specialisation
+
+5. Some hospitals host more than one transplant unit. 
+However some do not have a transplant unit.
+A hospital can have 0, 1 or many transplant units.
+
+- **Transplant Operation**:
+    - Involves a **Donor** [1:1] and a **Patient** [1:1].
+        - Encompasses one or more **Organs** [1:M].
+- **Donor**:
+    - May be associated with one or more **Transplant Operations** [1:M].
+- **Patient**:
+    - May be associated with one or more **Transplant Operations** [1:M].
+- **Organ**:
+    - Is involved in one or more **Transplant Operations** [M:1].
+- **Specialist Transplant Unit**:
+    - Is tied to one **Hospital** [1:1].
+    - Specialises in one type of **Organ** transplantation [o:1].
+    - Can handle other types of **Organ** transplants outside its specialization [o:M].
+- **Hospital**:
+    - Can host one or more **Specialist Transplant Units** [1:M].
+    - Not all hospitals have a **Transplant Unit** [o:1].
+
+`Hospital` -|---o-< `TransplantUnit`
+
+- One hospital can have 0, 1 or many Units.
+- A unit must have a hospital, and only 1.