Mysql算天下雨的表

Question

我想知道在一段时间内（雨＆gt; 0.1）咨询mysql会有多少天。

我使用此代码，但它让我回归所有日子，有雨和无雨

$result = mysqli_query($con,"SELECT City, count(Rain > '0.1') as Total FROM Meteo2 where Data BETWEEN '" . split($_POST["date6"]) ."' AND '" . split($_POST["date7"]) ."' group by City");

TKS

Answer 1

函数count()计算non-NULL值的数量。我想你想要sum()：

select sum(Rain > 0.1)
. . .

MySQL将布尔值视为整数，0表示false，1表示true。所以总和做你想要的，而不是数数。

Answer 2

$result = mysqli_query($con,"SELECT City, count(SELECT Rain FROM Meteo2 WHERE Rain > '0.1') as Total FROM Meteo2 where Data BETWEEN '" . split($_POST["date6"]) ."' AND '" . split($_POST["date7"]) ."' group by City");

Answer 3

按城市分组的雨量

$result = mysqli_query($con,"SELECT City, SUM(SELECT Rain FROM Meteo2 WHERE Rain > '0.1') as Total FROM Meteo2 where Data BETWEEN '" . split($_POST["date6"]) ."' AND '" . split($_POST["date7"]) ."' GROUP BY City");