Mysql GROUP_CONCAT 根据计数相乘

Question

I'm trying to make a mysql query that GROUP_CONCAT's all strings from the table 'shop_previews'. When running the following query however, it repeats it based on the amount of "timesBought".

select 
    `shop_items`.*, 
     group_concat(shop_previews.image) as images, 
     count(`shop_histories`.`shopId`) as `timesBought` 
from `shop_items`
left join `shop_previews` on `shop_previews`.`shopId` = `shop_items`.`id`
left join `shop_histories` on `shop_items`.`id` = `shop_histories`.`shopId`
group by `shop_items`.`id` 
order by `timesBought` desc

So if timesBought equals to two, and there was only one result from shop_previews.image, it would concat that one entry with itself, resulting in something like

https://example.com/example.png,https://example.com/example.png

Answer 1

GROUP_CONCAT()支持DISTINCT ：

GROUP_CONCAT(DISTINCT shop_previews.image) as images