Table DISPLAY_TAB below is a self-reference table that can contain both parent and child tabs. A parent tab can have multiple child tabs and a child tab can belong to multiple parents.
I'd like to establish a CASCADE DELETE relationship between main table and relationship table DISPLAY_TAB_GROUPING so when either parent or child tab is deleted - relationship is automatically deleted as well (just relationship, not actual tab record). So I am creating a FOREIGN KEY constrain on DISPLAY_TAB_GROUPING for fields TAB_ID_R_1 and TAB_ID_R_2 tables, referencing TAB_ID in DISPLAY_TAB table. And it works fine, it works fine when I add ON DELETE CASCADE for one of the relationship, but when I try it for both - it throws an error that this "May cause cycles or multiple cascade paths".
How do I set ON CASCADE DELETE for both relationships? I don't see how this can cause cycles - every time a record in main table is deleted only related record(s) in relationship tables should be deleted.
Read this KB article, which says the following among other things...
You receive this error message because in SQL Server, a table cannot appear more than one time in a list of all the cascading referential actions that are started by either a DELETE or an UPDATE statement. For example, the tree of cascading referential actions must only have one path to a particular table on the cascading referential actions tree.
To do what you want, the DISPLAY_TAB_GROUPING table would have to appear twice. I suggest you use a stored proc that implements your delete code instead.
来源：https://stackoverflow.com/questions/19910621/cascade-delete-in-many-to-many-self-reference-table