Question

这是我最初的有效查询：

DECLARE @total AS FLOAT;
SET @total =(SELECT COUNT(*) FROM Crimes)

SELECT
    Areas.Area,
    Areas.AreaName,
    COUNT(*) AS Total, 
    Round(CONVERT(float,(COUNT(*) / @total) * 100),3)
FROM Areas
INNER JOIN Crimes
    ON(Areas.Area = Crimes.Area)
GROUP BY
    Areas.AreaName,
    Areas.Area

我所做的唯一更改是将聚合函数重命名为“ Percent”，这就是说Area和AreaName两列存在无法绑定的问题，我不确定为什么。

新更改：

DECLARE @total AS FLOAT;
SET @total =(SELECT COUNT(*) FROM Crimes)
SELECT
    Areas.Area,
    Areas.AreaName,
    COUNT(*) AS Total,
    Round(CONVERT(float,(COUNT(*) / @total) * 100),3) AS Percent
FROM Areas
INNER JOIN Crimes
    ON(Areas.Area = Crimes.Area)
GROUP BY
    Areas.AreaName,
    Areas.Area

Answer 1

PERCENT是SQL Server中的关键字。尝试使用其他别名，例如Pct：

SELECT
    a.Area,
    a.AreaName,
    COUNT(*) AS Total,
    Round(CONVERT(float, (COUNT(*) / @total) * 100), 3) AS Pct
FROM Areas a
INNER JOIN Crimes c
    ON a.Area = c.Area
GROUP BY
    a.AreaName,
    a.Area;

请注意，我也向您的查询中引入了表别名，这使代码不太冗长，更易于阅读。

您也可以在方括号中使用[Percent]。但是，这带来了这样的风险，即有人在子查询您的查询时也必须转义该别名。因此，我宁愿完全避免为列名和表名使用关键字。

使用聚合函数在带有AS的SQL中命名列

1 个答案: