Oracle 820 ms two solution + explanation
Solution 1:\n1. Union IDs from both table (with saving duplicates)\n2. Select IDs from step 1 that occur once (IDs with name and salary will have duplicates)\n3
**Solution 1:**\n1. Union IDs from both table (with saving duplicates)\n2. Select IDs from step 1 that occur once (IDs with name and salary will have duplicates)\n3. Sort IDs from step 2\n```\nselect employee_id from (\n    select employee_id from employees\n    union all\n    select employee_id from salaries\n) tmp\ngroup by employee_id\nhaving count(employee_id) = 1\norder by employee_id\n```\n\n**Solution 2:**\n1. Find IDs from first table, thats not occur in second table\n2. Find IDs from second table, thats not occur in first table\n3. Union results from previous steps\n4. Sort IDs from step 3\n```\nselect employee_id from (\n    select e.employee_id from employees e\n    left join salaries s on e.employee_id = s.employee_id\n    where s.employee_id is NULL\n    union all\n    select s.employee_id from employees e\n    right join salaries s on e.employee_id = s.employee_id\n    where e.employee_id is NULL\n) tmp\norder by employee_id\n```
['Union Find', 'Oracle']