僅從昨天起從數據庫中選擇sql

Question

如何僅從昨天選擇我的sql數據庫？這裏是我的代碼：

 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 

我的數據庫名是timein和方式，輸入該INSERT完成的日期和時間。這裏是代碼：

 Database column : timein 

     Database insert looks like : 2012-9-6 9:11:35 

基本上我想只能從昨天選擇和COUNT。我如何才能從昨天的SQL數據庫中選擇COUNT？

Answer 1

試試這個添加一個條件爲昨天發生的一樣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 

或者你可以使用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 

Answer 2

您的查詢是沒有意義的。您正在進行user和visitors之間的交叉連接，然後僅對訪問者進行過濾。我懷疑你想要的東西，如：

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; 

的where子句，以獲得昨天的數據是：

WHERE date(timein) = date(NOW() - INTERVAL 1 DAY) 

或者，如果你在timein有一個指標：

WHERE timein >= date(NOW() - INTERVAL 1 DAY) and timein < date(NOW())