我有一个表,里面有一些图书的评级;
这些是我为测试这个查询而创建的一些虚拟记录;
ID BookID RatersID Rating Date
1 2 3 5 (date)
2 2 4 4 (date)
SELECT `RatersID`,
COUNT(*) AS `raters`, `Rating`, COUNT(*) AS `Ratings`
FROM
`BOOKS_ratings`
GROUP BY
`BookID`
当我运行查询时,我期望
BookID Raters Ratings
2 2 9
结果:
RatersID raters Rating Ratings
3 2 5 2
我不明白为什么会发生这种情况?///////////////////以上内容已得到解答
我已经得到了查询工作,但当试图在php中接收信息的数字是重复的
E。g Raters = 2 PHP显示22评分= 9
$getratingq = mysqli_query($con,"SELECT `RatersID`, COUNT(*) AS `Raters`, sum(Rating) AS `Ratings` FROM `BOOKS_ratings` WHERE `BookID` ='$bookid' GROUP BY `BookID` LIMIT 1") or die("Get ratings query error");
if($getrating = mysqli_fetch_array($getratingq))
{
echo $ratings = $getrating['Ratings'];
$raters= $getrating['Raters'];
$rating = $ratings/$raters;
$stars = floor("$rating");
}
您需要使用sum()
来获得评级的总和
SELECT
`BookID`,
COUNT(*) AS `raters`
sum(Rating) as Ratings
FROM
`BOOKS_ratings`
GROUP BY
`BookID`