MySQL的GROUP_CONCAT上加入行DISTINCT

Question

我有一個查詢誰是這樣的

SELECT 
producttemp.*, 
GROUP_CONCAT(colors.id) as color, 
GROUP_CONCAT(DISTINCT upc.UPC) as upc 
FROM producttemp 
INNER JOIN productcolor 
ON productcolor.productid=producttemp.id 
INNER JOIN upc 
ON upc.productid=producttemp.id 
INNER JOIN colors 
ON colors.id=productcolor.colorid 
INNER JOIN categorie 
ON categorie.id = producttemp.productcategorie 
GROUP BY producttemp.id 
LIMIT 5 

出於某種原因或antoher我在resultfield得到「色」重複的值，即「1,2,1,2」。爲什麼DISTINCT無法在連接的行上工作？有沒有機會解決或者我錯過了一個觀點？

Answer 1

嘗試DISTINCT上colors.id ::

SELECT 
producttemp.*, 
GROUP_CONCAT(DISTINCT colors.id) as color, 
GROUP_CONCAT(DISTINCT upc.UPC) as upc 
FROM producttemp 
INNER JOIN productcolor 
ON productcolor.productid=producttemp.id 
INNER JOIN upc 
ON upc.productid=producttemp.id 
INNER JOIN colors 
ON colors.id=productcolor.colorid 
INNER JOIN categorie 
ON categorie.id = producttemp.productcategorie 
GROUP BY producttemp.id 
LIMIT 5