我想按当前日期从不同的表中计算记录,并在新表中以具有不同列的一行返回。该代码将每三小时更新一条记录,并在当前日期更改时插入新记录。我在"created_at"列中有当前的日期和时间数据 (2013-05-20 14:12:12(。这是我当前的代码:
require_once('./db_connect.php');
$dbcon = new db;
//test to see if a specific field value is already in the DB
public function in_table($table,$where) {
$query = 'SELECT * FROM ' . $table . ' WHERE ' . $where;
$result = mysqli_query($this->dbh,$query);
$this->error_test('in_table',$query);
return mysqli_num_rows($result) > 0;
}
//running in background
while (true) {
$select= "SELECT (SELECT CURDATE()) AS time," .
"(SELECT COUNT(tweet_id) FROM tweets WHERE created_at= 'CURDATE() %') AS total_count," .
"(SELECT COUNT(fid) FROM fun WHERE ftime= 'CURDATE() %') AS f_count," .
"(SELECT COUNT(sid) FROM sad WHERE stime= 'CURDATE() %') AS s_count";
$results = mysqli_query( $dbcon, $select );
while($row = mysqli_fetch_assoc($result)) {
$time = $row['time'];
$total = $row['total_count'];
$fcount = $row['f_count'];
$scount = $row['s_count'];
$field_values = 'time = "' . $time . '", ' . 'total_count = ' . $total . ', ' . 'fun_count = ' . $fcount . ', ' . 'sad_count = ' . $scount;
if ($dbcon->in_table('count','time= "' . $time . '"')) {
$update = "UPDATE count SET $field_values WHEN time= '$time'";
mysqli_query( $dbcon, $update );
}
else {
$insert = "INSERT INTO count SET $field_values";
mysqli_query( $dbcon, $insert );
}
}
//update record every 3 hour
sleep(10800);
}
使用此代码,我无法获得计数记录。结果返回| 2013-05-18 | 0 | 0 | 0 |
。我该如何纠正此问题?
我不熟悉 PHP,但您可以使用以下方法检索今天任何时间的所有记录的计数:
SELECT COUNT(tweet_id)
FROM tweets
WHERE created_at >= curDate()
AND created_at < date_add(curDate(), interval 1 day)
相当于说
..
WHERE created_at >= (today at midnight *incusive*)
AND created_at < (tomorrow at midnight *exclusive*)
更新:
这种方法的优点是它对索引友好。虽然使用 WHERE DATE(Column) = currDate()
有效,但它可以阻止数据库对该列使用索引,从而使查询速度变慢。
替换您拥有以下内容的部分:
WHERE created_at= 'CURDATE() %'
有了这个:
WHERE DATE(created_at) = CURDATE()
您现有的 WHERE
子句正在将created_at
与字符串常量CURDATE() %
进行比较,它们永远不会匹配。
您正在与created_at= 'CURDATE() %'
进行比较,后者正在寻找确切的字符串,而不是函数的结果。如果字段created_at
是日期,则永远不会匹配。
而且,您正在为所有计数执行此操作。