✅ MySql
Using UNION\n\nSELECT employee_id\nFROM\n( SELECT employee_id FROM Employees\nUNION ALL \nSELECT employee_id FROM Salaries\n)emp\nGROUP BY employee_id\nHAVING C
Using **UNION**\n```\nSELECT employee_id\nFROM\n( SELECT employee_id FROM Employees\nUNION ALL \nSELECT employee_id FROM Salaries\n)emp\nGROUP BY employee_id\nHAVING COUNT(employee_id)=1\nORDER BY 1;\n```
['Union Find', 'MySQL']