如何修复PHP中的Datediff语法

问题描述：

I calling out value from database where Datediff from followupdate and NOW().

If the followupdate is happened before NOW(), it works, but if followupdate comes after NOW() it does't work.

This is my focus line. $re1 = mysqli_query($conn,"select booking.* from booking WHERE DATEDIFF( NOW(),followupdate ) <= 3 ;");

already try switch NOW() and followupdate back and forward.

date_default_timezone_set("Asia/Kuala_Lumpur");

$re1 = mysqli_query($conn,"select booking.* from booking WHERE DATEDIFF( NOW(),followupdate  ) <= 3 ;");
if(mysqli_num_rows($re1) > 0){
    while ($row = mysqli_fetch_array($re1) ){


     print "<tr style=\"\">      <td>".$row['booking_id']."</td>
";

p/s: assumed the followupdate is always larger than NOW()

Give me a simple code that can describe what to do. thanks

答

If you have already tried swapping positions and still getting failures I suggest you use

WHERE ABS( DATEDIFF( followupdate, NOW() ) ) <= 3

so the date difference can be either positive or negative and your comparison will continue to operate.

答

DATEDIFF(date1, date2) returns the result of date1 - date2 in days. If date2 is later, the result is negative.

SELECT DATEDIFF( DATE('2019-12-1'), NOW()); returns 330 today, on 2019-1-5.

You propably want:

WHERE DATEDIFF( followupdate, NOW() ) <= 3

如何修复PHP中的Datediff语法

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