Creating a Many-to-Many Relationship is easy in ServiceNow. However...with an example it is even easier!
In this post, I'll show an example "Test Case" Application that has an M2M relationship with "Test Case Steps".
This is a supplement to the wiki article on Creating a Many-to-Many Relationship.
https://wiki.servicenow.com/index.php?title=Creating_a_Many-to-Many_Relationship
Create Test Case Application
1. Create new application (UAT Testing)
2. Create New Table (Test Cases)
3. Personalize Form (Test Case Form)
4. Create New Table (Test Case Steps)
5. Personalize Form (Test Case Steps)
6. Turn on Auditing
Create M2M Relationship between Test Cases and Test Case Steps
1. Go to Many-to-Many Lists (Type sys_m2m.list in the Navigation Filter text)
2. Many-to-Many Lists (Click New)
3. Many-to-Many Lists (Add From and To Tables)
Note: if you add the From and To Tables, the rest will auto-fill in.
4. Personalize Related List (Test Cases)
Note: Go to Test Cases and add the Related List: Test Case Steps
5. Personalize Related List (Test Case Steps)
Note: Go to Test Case Steps and add the Related List: Test Cases
6. Personalize Related List Layout (Test Case Steps)
7. Personalize Related List Layout (Test Cases)
Results
1. Test Case Form
2. Test Case Steps Form