SQL：選擇列值至少出現N次的行？

Question

假設我有一個帶有兩列的SQL表“Celebrities”：“fname”和“lname”：

fname    | lname    
---------+-------  
Bill     | Clinton
Bill     | Gates
George   | Bush
George   | Clinton
Barack   | Obama

我想編寫一個查詢，返回表中每個人的名字和姓氏，其姓氏在“lname”列中至少出現兩次。 我該如何編寫這個SQL查詢？

Answer 1

SELECT fname, lname FROM Celebrities 
WHERE lname IN 
 (SELECT lname FROM Celebrities 
  GROUP BY lname HAVING COUNT (lname) >1)

Answer 2

使用JOIN：

SELECT a.*
  FROM CELEBRITIES a
  JOIN (SELECT c.lname
          FROM CELEBRITIES c
      GROUP BY c.lname
        HAVING COUNT(*) >= 2) b ON b.lname = a.lname

使用EXISTS：

SELECT a.*
  FROM CELEBRITIES a
 WHERE EXISTS (SELECT NULL
                 FROM CELEBRITIES c
                WHERE c.lname = a.lname
             GROUP BY c.lname
               HAVING COUNT(*) >= 2) 

Answer 3

select fname, lname
from 
  (
    select fname, lname, count(*) over(partition by lname) as lcount
    from Celebrities
  ) as S
where lcount > 1

在SQL Server 2008中測試。可能在支持count(*) over(...)其他DBMS中工作