Symptoms
On the form of table A, there is a related list missing the 'Edit' button. This related list is a many-to-many relationship between table A and table B.
Release
All
Cause
Although the name of the 'many-to-many relationship table' might indicate it is such type of table, this may not be the case. Opening this table in a List View from the related list ( cmd + right-click > 'Open new window') and examining the URL might suggest it's a 'many-to-many relationship' table because of the table's name format:
https://[instance-name].service-now.com/u_m2m_ATable_BTable_list.do?sysparm_query=problem%3D325790a2db8d3b006907f13bbf96196c%5E
Specifically, the u_m2m_ATable_BTable part. However, this table could have been given the u_m2m_ATable_BTable name from a user trying to build a many-to-many relationship table but using the wrong method to do so. Although the custom table might have been given the right reference fields to build a many-to-many relationship, additional field properties in the reference fields need to be set up that enables links to the parent tables (Tables A or Table B). The user is better served using the OOB method for building many-to-many relationship tables instead of going to System Definition > Tables.
Resolution
An easier way to build a many-to-many relationship table is to use provided OOB method that is specifically designed for these purposes
- Navigate to sys_m2m.list
- Hit the 'New' button
- Enter Table A in "From table" and Table B in "To table"
When you add this newly created table to the related list of either Table A or Table B, you will see the "New" and "Edit" button on either related list.
Additional Information
https://docs.servicenow.com/csh?topicname=t_CreateAManyToManyRelationship.html&version=latest
