MYSQL選擇更新鮮明的欄目，基於最低值

Question

我有下面的示例表數據：

id, price, product_id, default 
905928, 2.92, 1523, 0 
905929, 2.89, 1523, 0 
905930, 3.92, 1524, 0 
905931, 6.67, 1525, 0 
905932, 11.92, 1526, 0 
905933, 5.34, 1526, 0 
905934, 3.92, 1527, 0 
905935, 1.11, 1528, 0 

我想更新與1默認列，只要重複的產品ID組內價格最低的項目被標記。所以結果應該是這樣的：

id, price, product_id, default 
905928, 2.92, 1523, 0 
905929, 2.89, 1523, 1 
905930, 3.92, 1524, 1 
905931, 6.67, 1525, 1 
905932, 11.92, 1526, 0 
905933, 5.34, 1526, 1 
905934, 3.92, 1527, 1 
905935, 1.11, 1528, 0 
905936, 0.11, 1528, 1 
905937, 1.89, 1528, 0 

在此先感謝。

Answer 1

試試這個：

update yourtable a 
inner join 
(select product_id, min(price) minprice from 
yourtable 
group by product_id 
) b 
on a.product_id = b.product_id 
inner join 
(select product_id, price, min(id) minid from 
yourtable 
group by product_id, price 
) c 
on a.product_id = c.product_id and c.price = b.minprice 
set defaultvalue = 1 
where a.price = b.minprice 
and a.id = c.minid 

演示here。

第二個join用於在多個記錄的最低值爲price且product_id相同的情況下獲得最小值id。