MySQL 如果差异小于 0，则选择 0，否则选择差异

Question

我想获得 StartDate 和 EndDate 之间的差值，但如果差值小于 0，我需要值 0(EndDate 可能在 StartDate 之前)。有没有办法在不重复 ROUND() 表达式的情况下在 SELECT 中执行此操作？

SELECT StartDate, EndDate, 
IF(ROUND(TIMESTAMPDIFF(SECOND, StartDate, EndDate)/86400, 1) < 0, 0, ROUND(TIMESTAMPDIFF(SECOND, StartDate, EndDate)/86400, 1)) AS Duration
FROM table
WHERE StartDate <= '2016-06-02' AND EndDate >= '2016-06-01';

Answer 1

只需使用 GREATEST()得到 0 和差值中的较大者。

SELECT StartDate, EndDate, 
GREATEST(ROUND(TIMESTAMPDIFF(SECOND, StartDate, EndDate)/86400, 1), 0) AS Duration
FROM table
WHERE StartDate <= '2016-06-02' AND EndDate >= '2016-06-01';