Oracle vertical stack query (union/union all/minus/intersect)

Scenario 1: Find the same row in two or more tables. ( intersection )

SELECT empno,ename FROM emp

intersect

select empno,ename from emp_bonus;

 

Scenario 2: Find out the records in table 1 but not in table 2. For example, query all employees who have not received bonuses. ( difference set )

SELECT empno,ename FROM emp

minus

select empno,ename from emp_bonus;

 Thinking: Why not use not in or not exists

 

Scenario 3: Summarize all people. ( union )

union (will remove duplicate records, deduplication rule: all columns of the query have the same value)

union all (no deduplication)