在SQL中查找重複記錄

Question

我有一個包含以下用戶數據的大表。

social security number 
name 
address 

我想在表中查找 其中SSN等於所有可能的重複，但名字不是

我的嘗試是：

SELECT * FROM Table t1 
WHERE (SELECT count(*) from Table t2 where t1.name <> t2.name) > 1 

Answer 1

上SSN一個分組應該這樣做

SELECT 
    ssn 
FROM 
    Table t1 
GROUP BY 
    ssn 
HAVING COUNT(*) > 1 

..或者，如果你有每SSN很多行，只希望找到重名）

... 
HAVING COUNT(DISTINCT name) > 1 

編輯，哎呀，誤解

SELECT 
    ssn 
FROM 
    Table t1 
GROUP BY 
    ssn 
HAVING MIN(name) <> MAX(name) 

Answer 2

這將處理超過兩個記錄與重複ssn的：

select count(*), name from table t1, ( 
    select count(*) ssn_count, ssn 
    from table 
    group by ssn 
    having count(*) > 1 
) t2 
where t1.ssn = t2.ssn 
group by t1.name 
having count(*) <> t2.ssn_count