SQL查询获取值不止一次

Question

我需要查询我的数据库，以显示我的表内的姓氏出现三次以上的姓氏。例如：在我的学生表中，有3个姓'Smith'，4个'Johnson'，1个'Potter'。我的查询应该显示那些姓氏史密斯和约翰逊的记录，因为这些值的出现次数大于或等于3次。

任何人都可以指向我吗？我正在考虑使用COUNT（），但似乎无法考虑如何应用它？

Answer 1

对于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

对于MySQL：

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

Answer 4

从甲骨文（但在大多数SQL的DB 工作）：

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

附：这是更快一个，因为你没有选择withing选择方法这里

Answer 5

对于PostgreSQL：

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

Answer 6

这里所说的回答也相当考究https://stackoverflow.com/a/6095776/1869562但在测试时，我意识到它只返回姓氏。 如果您想要返回整个记录本身，该怎么办？ 做到这一点 （MySQL的）

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

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