試圖在同一個查詢中用不同的where子句指定不同的日期範圍來總結一個字段「計數」三次？

Question

SELECT DeviceID as "Printer Name", 
    (SELECT SUM(Count) WHERE DATE >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)as "7 Day Count", 
    (SELECT SUM(Count) WHERE DATE >= DATE_SUB(CURDATE(), INTERVAL 30 DAY)as "30 Day Count" 
FROM printer_stats.Statistics 
GROUP BY DeviceID 

這是行不通的，想要接下來嘗試的一些輸入。

Answer 1

使用SUM(CASE WHEN condition THEN Count ELSE 0 END)：

SELECT 
    DeviceID as "Printer Name", 
    SUM(CASE WHEN DATE >= CURDATE() - INTERVAL 7 DAY THEN Count ELSE 0 END) AS "7 Day Count", 
    SUM(CASE WHEN DATE >= CURDATE() - INTERVAL 30 DAY THEN Count ELSE 0 END) AS "30 Day Count", 
FROM printer_stats.Statistics 
WHERE DATE >= CURDATE() - INTERVAL 30 DAY 
GROUP BY DeviceID