Add example of unary relationship

3 files changed, 24 insertions, 0 deletions

diff --git a/assignments/1/README.md b/assignments/1/README.md
index a91c1e5..bb05688 100644
--- a/assignments/1/README.md
+++ b/assignments/1/README.md
@@ -63,6 +63,13 @@ b. Weak entity
 
 c. Unary relationship
 
+  A unary relationship is a relationship between the instances of a single entity type.
+  This is a self referential or recursive relationship.
+
+  Group is subgroup of group.
+
+  ![unary relationship example](./unary-relationship.png)
+
 ### Question 3 (20 marks)
 
 As an independent consultant, you have a contract with Athabasca University to develop an application to support
diff --git a/assignments/1/unary-relationship.png b/assignments/1/unary-relationship.png
new file mode 100644
index 0000000..a2d7ecb
--- /dev/null
+++ b/assignments/1/unary-relationship.png
diff --git a/assignments/1/unary-relationship.uml b/assignments/1/unary-relationship.uml
new file mode 100644
index 0000000..91c0425
--- /dev/null
+++ b/assignments/1/unary-relationship.uml
@@ -0,0 +1,17 @@
+@startuml
+!define Table(name,desc) class name as "desc" << (T,#FFAAAA) >>
+!define primary_key(x) <b>x</b>
+!define unique(x) <color:green>x</color>
+!define not_null(x) <u>x</u>
+hide methods
+hide stereotypes
+
+' entities
+Table(group, "group") {
+  primary_key(id) INTEGER
+  not_null(name) VARCHAR[255]
+}
+
+' relationships
+group --> group : "A group may be a sub group of another group"
+@enduml