[oracle] 외례키 내용 검색하기

//예제1
SELECT 
    count(Emp_Name)
FROM 
    Sales_DB a JOIN 
    Emp_DB b ON a.Emp_ID = b.Emp_ID
where 
    emp_name = '조인성';
 
 
//예제2
SELECT 
    Emp_Name, 
    count(Emp_Name)
FROM 
    Sales_DB a JOIN 
    Emp_DB b ON a.Emp_ID = b.Emp_ID
group by 
    emp_name