減少查找重複記錄查詢執行時間

Question

我有3個lac的記錄。我需要統計重複的記錄並返回所有重複的記錄（例如，如果exam​​ple@example.com是10次，然後返回所有10條記錄的重複數爲10）

我已經創建了查詢，但需要15秒的時間。任何建議減少時間？

SELECT g.guest_name, g.email, b.totalCount AS duplicate_guest 
FROM guest g 
INNER JOIN (SELECT email, COUNT(Id) AS totalCount FROM guest GROUP BY email) b ON g.email = b.email 

Answer 1

需要通過添加有條件如下面的查詢，以減少對加盟條件的數據。

還要確保應該對電子郵件列的索引來優化它

SELECT g.guest_name, g.email, b.count as duplicate_guests 
FROM guest g 
INNER JOIN 
(
    SELECT email, COUNT(Id) AS count 
    FROM guest 
    GROUP BY email 
    HAVING count(*) > 1 
) b ON g.email = b.email 

Answer 2

只需添加HAVING count(*) > 1到內選擇

SELECT g.guest_name, g.email, b.totalCount AS duplicate_guest 
FROM guest g 
INNER JOIN 
(
    SELECT email, COUNT(Id) AS totalCount 
    FROM guest 
    GROUP BY email 
    HAVING count(*) > 1 
) b ON g.email = b.email