naturnal 非常嚴謹 (幹 但是只有oracle有 MSSQL沒有阿)
--Oracle : naturnal join :兩個相同欄位     相同吻合才抓出

--Oracle : using  使用部分吻合就抓出
--ANSI inner
--ANSI outer left 看table1
--ANSI outer right 看table2
--ANSI full outer 兩個表都看 兩個表都抓



--Oracle : naturnal join :兩個相同欄位   
SELECT employee_id,department_id,department_name
FROM employees natural join departments;


--Oracle : using
SELECT employee_id,department_id,department_name
FROM employees join departments  using(department_id);

--ANSI inner
SELECT e.employee_id,e.department_id,d.department_name
FROM employees e  inner join departments d
on   e.department_id=d.department_id;


--ANSI outer left
SELECT e.employee_id,e.department_id,d.department_name
FROM employees e left outer join departments d
on   e.department_id=d.department_id;


--ANSI outer right
SELECT e.employee_id,e.department_id,d.department_name
FROM employees e right outer join departments d
on   e.department_id=d.department_id;


--ANSI full outer
SELECT e.employee_id,e.department_id,d.department_id,d.department_name
FROM employees e full outer join departments d
on   e.department_id=d.department_id;



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