清理數據庫記錄

Question

我有一個沒有真正規範化的數據庫，所以我回去嘗試使它更好一點。現在我們有以下列：

FirstName | LastName | SchoolYear | Grade | SchoolId | Games Played 
Bob  | Smith | 2010  | Fr | 245  | 3 
Tina  | Johnson | 2010  | So | 2894  | 10 
Bob  | Smith | 2010  | Fr | 245  | 3 

我如何找到有2人同名，學年，年級和學校ID的學校？他們看起來像數據庫中的副本（所有列都是相同的），但每個玩家只有一行遊戲每年玩。這就是我知道學校裏有類似的人，會有兩行信息相同。

我正在使用SQL Server 2008

謝謝！

Answer 1

如果我正確理解你的問題，這個查詢：

SELECT FirstName, LastName, SchoolYear, Grade, SchoolId 
FROM <your table> 
GROUP BY FirstName, LastName, SchoolYear, Grade, SchoolId 
HAVING COUNT(*) > 1 

這將基本上找到所有的（名字，姓氏，學年，年級，SchoolId）中存在的多套一個記錄。

如果你只在上面記錄SchoolId的興趣，然後一起去：

SELECT DISTINCT SchoolId 
FROM <your table> 
GROUP BY FirstName, LastName, SchoolYear, Grade, SchoolId 
HAVING COUNT(*) > 1 

Answer 2

select count(*), FirstName, LastName, SchoolYear, Grade, SchoolId 
from mytable 
group by FirstName, LastName, SchoolYear, Grade, SchoolId 
order by 1 desc 

Answer 3

select FirstName, LastName, SchoolYear, Grade, SchoolId 
from Student 
group by FirstName, LastName, SchoolYear, Grade, SchoolId 
having count(*) > 1 

Answer 4

簡單GROUP BY和HAVING應該做的：

SELECT SchoolId 
FROM YourTable 
GROUP BY FirstName, LastName, SchoolYear, Grade, SchoolId, [Games Played] 
HAVING COUNT(*) = 2 

請注意，您可能需要使用HAVING COUNT(*) > 1如果你想找到所有重複學生的學校。

Answer 5

SELECT FirstName, 
     LastName, 
     SchoolYear, 
     Grade, 
     SchoolId, 
     (CASE WHEN COUNT(*) > 1 THEN 'Yes' ELSE 'No' END) AS 'Repeat?' 
FROM <table_name> 
GROUP BY FirstName, LastName, SchoolYear, Grade, SchoolId