查詢返回重複的記錄頻率

Question

我有一個「更新」表中可以包含重複的描述，我想用自己的計數一起返回重複的，所以我創造了這個查詢：

SELECT description, count(description) AS count 
FROM updates INNER JOIN participations ON participations.update_id = updates.id 
INNER JOIN customer ON customer.id = participations.customer_id 
INNER JOIN garages ON garages.id = customer.garage_id 
WHERE (updates.created_at >= DATE_SUB(CURDATE(), INTERVAL 6 MONTH)) 
AND garages.`id` = 1 
GROUP BY description 
ORDER BY count desc 
LIMIT 10 

計數返回的不是我所期待的。我相信之所以會這樣，是因爲許多客戶可以共享更新，所以我得到重複的原因是表中存在實際的重複項，並且因爲同一更新記錄多次返回。如何修復查詢以便它只計算更新表中的實際重複描述字段。由於

Answer 1

你可以重寫查詢使用EXISTS，因爲你需要的客戶只是去車庫:-)

SELECT description, count(description) AS count 
FROM updates 
WHERE (updates.created_at >= DATE_SUB(CURDATE(), INTERVAL 6 MONTH)) 
AND EXISTS (select null from participations INNER JOIN customer ON customer.id = participations.customer_id WHERE participations.update_id = updates.id AND customer.garage_id = 1) 
GROUP BY description 
ORDER BY count desc 
LIMIT 10