从更新后的数据库中选择数据

Question

In my database i have column vv that had values in ""09.12.2019 12:55:50"". So i dont want remove my records and updated my data to this format 2019-12-09 12:55:50 but i am not getting any result against $result2. I am even not getting any error. The input values i am selecting has data against it in database but i am getting the output in $result2.

<?php
 include("includes\conn.php"); 
 $start = $_POST['start_date'];
 $temp_date= substr($start, 0, 10);
 $temp_date1= substr($start, 11, 17);
 $final= $temp_date.' '.$temp_date1;
 $result = mysqli_query($con,"$result = mysqli_query($con,"UPDATE `data` SET `vv` = STR_TO_DATE(REPLACE(`vv`, '.', '-'), '%d-%m-%Y %H:%i:%s')");");
 $result2 = mysqli_query($con,"SELECT * FROM data WHERE vv = '$final'");
 print_r($result2);
?>

Your Kind help is needed!

Answer 1

Not sure what do you produce in $final variable, but assuming you have there a string that represent some proper datetime like 2019-12-09 12:55:50 , then you need to execute the following UPDATE query that will convert ""09.12.2019 12:55:50"" to 2019-12-09 12:55:50 strings:

UPDATE `data` SET `vv` = STR_TO_DATE(REPLACE(`vv`, '"', ''), '%d.%m.%Y %H:%i:%s')

However, executing an UPDATE on every POST request in order to get a SELECT result afterwards is simply very bad approach. Better consider to ALTER your table and convert this nasty vv column into real datetime datatype format once you convert all the strings there.