SQL查詢獲取值不止一次

Question

我需要查詢我的數據庫，以顯示我的表內的姓氏出現三次以上的姓氏。例如：在我的學生表中，有3個姓'Smith'，4個'Johnson'，1個'Potter'。我的查詢應該顯示那些姓氏史密斯和約翰遜的記錄，因爲這些值的出現次數大於或等於3次。

任何人都可以指向我嗎？我正在考慮使用COUNT（），但似乎無法考慮如何應用它？

Answer 1

對於SQL Server 2005+

;WITH T AS 
(
SELECT *, 
     COUNT(*) OVER (PARTITION BY Lastname) as Cnt 
FROM Students 
) 
SELECT * /*TODO: Add column list. Don't use "*"     */ 
FROM T 
WHERE Cnt >= 3 

Answer 2

SELECT LASTNAME, COUNT(*) 
FROM STUDENTS 
GROUP BY LASTNAME 
ORDER BY COUNT(*) DESC 

Answer 3

對於MySQL：

SELECT lastname AS ln 
    FROM 
    (SELECT lastname, count(*) as Counter 
    FROM `students` 
    GROUP BY `lastname`) AS tbl WHERE Counter > 2 

Answer 4

從甲骨文（但在大多數SQL的DB 工作）：

SELECT LASTNAME, COUNT(*) 
FROM STUDENTS 
GROUP BY LASTNAME 
HAVING COUNT(*) >= 3 

附：這是更快一個，因爲你沒有選擇withing選擇方法這裏

Answer 5

對於PostgreSQL：

SELECT * AS rec 
FROM (
    SELECT lastname, COUNT(*) AS counter 
    FROM students 
    GROUP BY lastname) AS tbl 
WHERE counter > 1; 

Answer 6

這裏所說的回答也相當考究https://stackoverflow.com/a/6095776/1869562但在測試時，我意識到它只返回姓氏。 如果您想要返回整個記錄本身，該怎麼辦？ 做到這一點 （MySQL的）

SELECT * 
FROM `beneficiary` 
WHERE `lastname` 
IN (

    SELECT `lastname` 
    FROM `beneficiary` 
    GROUP BY `lastname` 
    HAVING COUNT(`lastname`) >1 
)