SQL 查询返回 MAX 的多个计数（年龄组）答案

【问题标题】：SQL Query Return MAX of multiple Counts (Age Groups)SQL 查询返回 MAX 的多个计数（年龄组）
【发布时间】：2022-01-23 07:31:56
【问题描述】：

我正在尝试完成此查询以仅返回记录最多的年龄组：

SELECT 
       COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 18 AND 29 THEN a.Data_Nasc END) AS '18-29',
       COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 30 AND 39 THEN a.Data_Nasc END) AS '30-39',
       COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 40 AND 49 THEN a.Data_Nasc END) AS '40-49',
       COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 50 AND 59 THEN a.Data_Nasc END) AS'50-59',
       COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) > 60 THEN a.Data_Nasc END) AS '>60'
FROM Cliente a
    JOIN Encomenda b ON b.NIF_Cliente = a.NIF_Cliente
WHERE b.NIF_Inst <> 999999999

此时查询返回：

18-29 30-39 40-49 50-59  >60
  9     19   11     5     18

记录最多的年龄段是30-39岁，所以想回归的就是那个。

谁能帮忙找出最好的解决方法？

【问题讨论】：

标签： sql count max

【解决方案1】：

您可以使用UNION 合并结果集并选择最顶部的结果

SELECT top 1 col1, (col) from (
    SELECT '18-29' as col1,  COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 18 AND 29 THEN a.Data_Nasc END) as col         
    FROM Cliente a
    JOIN Encomenda b ON b.NIF_Cliente = a.NIF_Cliente
    WHERE b.NIF_Inst <> 999999999
    union all
    SELECT '30-39' as col1, COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 30 AND 39 THEN a.Data_Nasc END) as col
    FROM Cliente a
    JOIN Encomenda b ON b.NIF_Cliente = a.NIF_Cliente
    WHERE b.NIF_Inst <> 999999999
    union all
    SELECT '40-49' as col1, COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 40 AND 49 THEN a.Data_Nasc END) as col
    JOIN Encomenda b ON b.NIF_Cliente = a.NIF_Cliente
    WHERE b.NIF_Inst <> 999999999
    union all
    SELECT '50-59' as col1, COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 50 AND 59 THEN a.Data_Nasc END) as col    
    FROM Cliente a
    JOIN Encomenda b ON b.NIF_Cliente = a.NIF_Cliente
    WHERE b.NIF_Inst <> 999999999
    union all
    SELECT '>60' as col1, COUNT(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) > 60 THEN a.Data_Nasc END) as col
    FROM Cliente a
    JOIN Encomenda b ON b.NIF_Cliente = a.NIF_Cliente
    WHERE b.NIF_Inst <> 999999999) as t
ORDER BY col DESC

【讨论】：

首先感谢您的快速帮助。我已经测试了您的解决方案，但它只是给了我最大的记录总数，它没有确定它属于哪个年龄段。我需要获得最大记录以及它属于哪个年龄段。

【解决方案2】：

SELECT 
       sum(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 18 AND 29 THEN 1 END) AS '18-29',
       sum(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 30 AND 39 THEN 1 END) AS '30-39',
       sum(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 40 AND 49 THEN 1 END) AS '40-49',
       sum(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) BETWEEN 50 AND 59 THEN 1 END) AS'50-59',
       sum(CASE WHEN DATEDIFF(YEAR, a.Data_Nasc, GETDATE()) > 60 THEN 1 END) AS '>60'
FROM Cliente a
    JOIN Encomenda b ON b.NIF_Cliente = a.NIF_Cliente
WHERE b.NIF_Inst <> 999999999

【讨论】：