爲什麼在這種情況下使用Min或Max會產生不同數量的結果？

Question

我想爲每個有至少1條評論的企業選擇最新評論。在一個單獨的查詢中，我試圖爲每個有至少1條評論的企業選擇最早的評論。

下面的查詢與我在第二次使用Max時使用Max相反。然而，他們產生了不同數量的結果（MAX的MIN & 673有1180個結果）。很困惑？？？誰能幫

SELECT comment.bis_id, comment.comment, comment.date 
FROM comment 
GROUP BY comment.bis_id 
HAVING comment.date = MIN(comment.date) 


SELECT comment.bis_id, comment.comment, comment.date 
FROM comment 
GROUP BY comment.bis_id 
HAVING comment.date = MAX(comment.date) 

Answer 1

在這種情況下，你應該使用這些查詢 -

SELECT c1.* FROM comment c1 
    JOIN (SELECT bis_id, MIN(date) date FROM comment GROUP BY bis_id) c2 
ON c1.bis_id = c2.bis_id AND c1.date = c2.date; 

SELECT c1.* FROM comment c1 
    JOIN (SELECT bis_id, MAX(date) date FROM comment GROUP BY bis_id) c2 
ON c1.bis_id = c2.bis_id AND c1.date = c2.date;