PostgreSQL JSON Functions: Resolving Multiple-Item Cardinality Issues

PostgreSQL error 22034 occurs when SQL/JSON functions receive multiple results from path expressions when expecting a single item—a common challenge with wildcard expressions and nested structures. Mastering cardinality constraints through explicit indexing, WITH ARRAY WRAPPER, and set-returning functions is essential for reliable JSON querying in PostgreSQL 15+. Validating JSON paths before deployment prevents runtime failures and ensures query reliability.