relationships Shipped

What this lens looks for

Validates one-to-many relationships via FK on child table, enforces many-to-many via join tables (never comma-separated lists), evaluates polymorphic FK patterns (discriminator column vs supertype table), assesses self-referential relationships, and reviews tree hierarchy approaches.

What its verifier checks

• One-to-many modeled as FK on child table, never as repeating group or array
• Many-to-many always uses explicit join table (with composite PK of both FKs or own PK + unique constraint)
• Polymorphic relationships justified: discriminator column approach chosen over supertype table with rationale
• Polymorphic discriminator column has CHECK constraint listing allowed types
• If supertype table used for polymorphic: base table PK correctly referenced by all subtypes
• Self-referential FKs (e.g., parent_id in same table) have index on FK column and ON DELETE documented
• Tree hierarchies approach documented: adjacency list (parent pointer), closure table, or nested sets
• Adjacency list used for shallow trees; closure table for querying deep hierarchies; nested sets only if frequent hierarchical queries