HQL Query to check if size of collection is 0 or empty

Using IS EMPTY should work (I would favor a JPQL syntax):

SELECT u FROM User u WHERE u.status = 1 AND u.appointments IS EMPTY

If it doesn’t, please show the generated SQL.

References

• Hibernate Core Reference Guide
  • 14.10. Expressions
• JPA 1.0 specification
  • Section 4.6.11 “Empty Collection Comparison Expressions”