diff --git a/.obsidian/workspace b/.obsidian/workspace
index 533def9..ccf6c8d 100644
--- a/.obsidian/workspace
+++ b/.obsidian/workspace
@@ -9,7 +9,7 @@
         "state": {
           "type": "markdown",
           "state": {
-            "file": "School/Development/SQL Database.md",
+            "file": "School/Development/Primary Key.md",
             "mode": "source"
           }
         }
@@ -68,7 +68,7 @@
             "state": {
               "type": "backlink",
               "state": {
-                "file": "School/Development/SQL Database.md",
+                "file": "School/Development/Primary Key.md",
                 "collapseAll": false,
                 "extraContext": false,
                 "sortOrder": "alphabetical",
@@ -87,6 +87,7 @@
   },
   "active": "bc6e8ad9aa0f44c3",
   "lastOpenFiles": [
+    "School/Development/Primary Key.md",
     "School/Development/SQL Database.md",
     "School/Analyse/OSI Model.md",
     "School/Analyse/Images/OSI-model.png",
@@ -95,7 +96,6 @@
     "School/Analyse/Comminucation Mediums.md",
     "School/Analyse/Network Types.md",
     "School/Analyse/Network Hardware.md",
-    "School/Analyse/Packet.md",
-    "School/Analyse/Untitled.md"
+    "School/Analyse/Packet.md"
   ]
 }
\ No newline at end of file
diff --git a/School/Development/Primary Key.md b/School/Development/Primary Key.md
new file mode 100644
index 0000000..53fc720
--- /dev/null
+++ b/School/Development/Primary Key.md	
@@ -0,0 +1,2 @@
+# Primary Key
+A Primary key is a [[Constraint]]  
\ No newline at end of file
diff --git a/School/Development/SQL Database.md b/School/Development/SQL Database.md
index bc5337f..f91eb00 100644
--- a/School/Development/SQL Database.md	
+++ b/School/Development/SQL Database.md	
@@ -25,10 +25,4 @@ An entity contains attributes that have values. For example, an entity Person ma
 
 ## Entity Set
 
-A entity set is a collection of entities that share the same attributes. The entities within the set are distinguishable from each other because the values that the attributes have differ.
-
-
-
-
-
-
+A entity set is a collection of entities that share the same attributes. The entities within the set are distinguishable from each other because the values that the attributes have differ. Most of the time this is done via a [[Primary Key]] constraint.
\ No newline at end of file