如何（或可以）在多列上选择DISTINCT？

SELECT DISTINCT a,b,c FROM t


是 大致 等效于：

SELECT a,b,c FROM t GROUP BY a,b,c


习惯GROUP BY语法是一个好主意，因为它更强大。

对于您的查询，我会这样做：

UPDATE sales
SET status='actIVE'
WHERE id IN
(
SELECT id
FROM sales S
INNER JOIN
(
SELECT saleprice, saledate
FROM sales
GROUP BY saleprice, saledate
HAVING COUNT(*) = 1
) T
ON S.saleprice=T.saleprice AND s.saledate=T.saledate
)