diff --git a/src/models/Address.ts b/src/models/Address.ts
index 59e6570..ccc2c70 100644
--- a/src/models/Address.ts
+++ b/src/models/Address.ts
@@ -25,7 +25,7 @@ export class Address {
   /**
    * The address's description.
    */
-  @Column()
+  @Column({nullable: true})
   @IsString()
   @IsOptional()
   description?: string;
@@ -43,7 +43,7 @@ export class Address {
    * The address's second line.
    * Containing optional information.
    */
-  @Column()
+  @Column({nullable: true})
   @IsString()
   @IsOptional()
   address2?: string;
diff --git a/src/models/GroupContact.ts b/src/models/GroupContact.ts
index 58a07a7..745174f 100644
--- a/src/models/GroupContact.ts
+++ b/src/models/GroupContact.ts
@@ -5,6 +5,7 @@ import {
   IsNotEmpty,
   IsOptional,
   IsPhoneNumber,
+  IsPositive,
   IsString,
 } from "class-validator";
 import { Address } from "./Address";
@@ -36,7 +37,7 @@ export class GroupContact {
    * The contact's middle name.
    * Optional
    */
-  @Column()
+  @Column({nullable: true})
   @IsOptional()
   @IsString()
   middlename?: string;
@@ -45,7 +46,7 @@ export class GroupContact {
    * The contact's last name.
    */
   @Column()
-  @IsOptional()
+  @IsNotEmpty()
   @IsString()
   lastname: string;
 
@@ -61,7 +62,7 @@ export class GroupContact {
    * The contact's phone number.
    * Optional
    */
-  @Column()
+  @Column({nullable: true})
   @IsOptional()
   @IsPhoneNumber("DE")
   phone?: string;
@@ -70,7 +71,7 @@ export class GroupContact {
    * The contact's email address.
    * Optional
    */
-  @Column()
+  @Column({nullable: true})
   @IsOptional()
   @IsEmail()
   email?: string;
diff --git a/src/models/Participant.ts b/src/models/Participant.ts
index 2f4327b..bcbf5ca 100644
--- a/src/models/Participant.ts
+++ b/src/models/Participant.ts
@@ -5,6 +5,7 @@ import {
   IsNotEmpty,
   IsOptional,
   IsPhoneNumber,
+  IsPositive,
   IsString,
 } from "class-validator";
 import { Address } from "./Address";
@@ -35,7 +36,7 @@ export abstract class Participant {
    * The participant's middle name.
    * Optional
    */
-  @Column()
+  @Column({nullable: true})
   @IsOptional()
   @IsString()
   middlename?: string;
@@ -44,7 +45,7 @@ export abstract class Participant {
    * The participant's last name.
    */
   @Column()
-  @IsOptional()
+  @IsNotEmpty()
   @IsString()
   lastname: string;
 
@@ -52,7 +53,6 @@ export abstract class Participant {
    * The participant's address.
    * Optional
    */
-  @IsOptional()
   @ManyToOne(() => Address, address => address.participants)
   address?: Address;
 
@@ -60,7 +60,7 @@ export abstract class Participant {
    * The participant's phone number.
    * Optional
    */
-  @Column()
+  @Column({nullable: true})
   @IsOptional()
   @IsPhoneNumber("DE")
   phone?: string;
@@ -69,7 +69,7 @@ export abstract class Participant {
    * The participant's email address.
    * Optional
    */
-  @Column()
+  @Column({nullable: true})
   @IsOptional()
   @IsEmail()
   email?: string;
diff --git a/src/models/ScanStation.ts b/src/models/ScanStation.ts
index 4415ebc..fd30a34 100644
--- a/src/models/ScanStation.ts
+++ b/src/models/ScanStation.ts
@@ -25,10 +25,10 @@ export class ScanStation {
   /**
    * The station's description.
    */
-  @Column()
-  @IsNotEmpty()
+  @Column({nullable: true})
+  @IsOptional()
   @IsString()
-  description: string;
+  description?: string;
 
   /**
    * The track this station is associated with.
diff --git a/src/models/Track.ts b/src/models/Track.ts
index eda6def..ce4693c 100644
--- a/src/models/Track.ts
+++ b/src/models/Track.ts
@@ -20,7 +20,7 @@ export class Track {
   @PrimaryGeneratedColumn()
   @IsOptional()
   @IsInt()
-  id: number;
+  id: number;;
 
   /**
    * The track's name.
diff --git a/src/models/User.ts b/src/models/User.ts
index d946500..fce74e8 100644
--- a/src/models/User.ts
+++ b/src/models/User.ts
@@ -11,10 +11,10 @@ export class User {
   /**
      * autogenerated unique id (primary key).
      */
-  @PrimaryGeneratedColumn()
-  @IsOptional()
-  @IsInt()
-  id: number;
+    @PrimaryGeneratedColumn()
+    @IsOptional()
+    @IsInt()
+    id: number;
 
   /**
      * autogenerated uuid
diff --git a/src/models/UserAction.ts b/src/models/UserAction.ts
index 7f6dc43..ea794a5 100644
--- a/src/models/UserAction.ts
+++ b/src/models/UserAction.ts
@@ -41,7 +41,7 @@ export class UserAction {
   /**
    * The description of change (before-> after; e.g. distance:15->17)
    */
-  @Column()
+  @Column({nullable: true})
   @IsOptional()
   @IsString()
   changed: string;
diff --git a/src/models/UserGroup.ts b/src/models/UserGroup.ts
index 5a19713..ae014e2 100644
--- a/src/models/UserGroup.ts
+++ b/src/models/UserGroup.ts
@@ -37,8 +37,8 @@ export abstract class UserGroup {
   /**
    * The group's description
    */
-  @Column()
+  @Column({nullable: true})
   @IsOptional()
   @IsString()
-  description: string;
+  description?: string;
 }
\ No newline at end of file