如何仅从昨天开始选择sql数据库？这是我的代码：
SELECT *, COUNT(visitors.usr_id) as usr_count FROM user, visitors WHERE visitors.usr_id = $usr_id GROUP BY $usr_id ORDER BY usr_count LIMIT 1
我的数据库名称是timein，它输入INSERT完成日期和时间的方式。这是代码：
Database column : timein
Database insert looks like : 2012-9-6 9:11:35
基本上，我希望能够选择和计数从昨天开始。如何仅从昨天开始从sql数据库中选择计数？
您的查询没有意义。您正在user和visitors之间进行交叉联接，然后仅对访问者进行筛选。我怀疑你想要这样的东西：
SELECT *, COUNT(visitors.usr_id) as usr_count
FROM user join
visitors
on visitors.usr_id = user.usr_id
WHERE user.usr_id = $usr_id
GROUP BY $usr_id
ORDER BY usr_count
LIMIT 1;
获取昨天数据的where子句是：
WHERE date(timein) = date(NOW() - INTERVAL 1 DAY)
或者，如果您在timein:上有索引
WHERE timein >= date(NOW() - INTERVAL 1 DAY) and timein < date(NOW())
试试这个为昨天添加一个条件，比如timein <= NOW() - INTERVAL 1 DAY , timein >= NOW() - INTERVAL 2 DAY;
SELECT *, COUNT(visitors.usr_id) as usr_count
FROM user, visitors
WHERE visitors.usr_id = $usr_id
AND timein <= NOW() - INTERVAL 1 DAY
AND timein >= NOW() - INTERVAL 2 DAY
GROUP BY $usr_id
ORDER BY usr_count
LIMIT 1
或者您可以使用BETWEEN
SELECT *, COUNT(visitors.usr_id) as usr_count
FROM user, visitors
WHERE visitors.usr_id = $usr_id
AND timein BETWEEN NOW() - INTERVAL 1 DAY AND NOW() - INTERVAL 2 DAY;
GROUP BY $usr_id
ORDER BY usr_count
LIMIT 1