当我尝试这个查询时:
SELECT DATE_ADD(upg_date, INTERVAL 30 DAY) AS 'upgrade_date'
WHERE id=12345
它返回给我正确值的记录,但是当我添加这样的条件时:
SELECT DATE_ADD(upg_date, INTERVAL 30 DAY) AS 'upgrade_date'
WHERE id=12345
AND 'upgrade_date' < NOW()
它返回一个空的结果集。但价值upgrade_date
低于当前日期。
怎么了?