好的，我有以下MySQL查询：
SELECT COUNT(*) FROM `dates` WHERE firstDate IS NOT NULL AND secondDate IS NOT NULL
AND DATEDIFF(secondDate, firstDate) >= 30
该查询返回9的值。然后我使用以下查询：
SELECT COUNT(*) FROM `dates` WHERE firstDate IS NOT NULL AND secondDate IS NOT NULL
AND DATEDIFF(secondDate, firstDate) >= 90
第二个查询返回12的结果。怎么可能呢？这两个日期都是MySQL数据库中的日期数据类型。
最佳答案
试着做这个
SELECT firstDate, secondDate, DATEDIFF(secondDate, firstDate) AS diff
FROM `dates` WHERE firstDate IS NOT NULL AND secondDate IS NOT NULL
AND DATEDIFF(secondDate, firstDate) >= 30
SELECT firstDate, secondDate, DATEDIFF(secondDate, firstDate) AS diff
FROM `dates` WHERE firstDate IS NOT NULL AND secondDate IS NOT NULL
AND DATEDIFF(secondDate, firstDate) >= 90
您将看到实际的行列表，而不是结果行的计数。
那也许能帮你弄清楚这件事。