Employees Without Certifications

Return employees that appear in Skills but have no certification, ordered by name.

Table schema

Skills(emp VARCHAR(10), skill VARCHAR(10))
Certs(emp VARCHAR(10), cert VARCHAR(10), expires DATE)

Sample data

Skills
emp | skill
Ann | SQL
Ann | Python
Ann | Java
Bob | SQL
Bob | Python
Cy | SQL

Certs
emp | cert | expires
Ann | AWS | 2026-12-01
Bob | AWS | 2026-11-15
Bob | GCP | 2027-05-01