运行此代码后，为什么我的SQL表数据会被删除？

I have this code that I want to run and it's connected to my database and it uses to show the values on the table but every time I do an UPDATE query.

It updates the rest of the row with zeros except the one I've chosen. I want to keep my numbers on the row but only update the one that i chose but I can't figure it out how to!

I initialized the table with a row with Zeros (0s) and then with my web page application I want to change those values.

But if I have another value on the rest of the columns and I want to change this one, the rest of the values go to zero (the initial state of the table) (I don't know how to explain it better I think)

<?php 
                      $showData = ("SELECT * FROM horario");
                      if ($new_user_activity['data'] == 'Seg' ) {
                          $segHora = $new_user_activity['horas'];
                      }
                          $sql = ("UPDATE horario SET seg=$segHora WHERE id=1");
                          if(!mysqli_query($conn,$sql)) {
                            echo("ERRO NA QUERY" );
                          }
                          else {
                            if(mysqli_query($conn,$sql)){
                              $sqlData = mysqli_query($conn,$showData);
                              while ($row = mysqli_fetch_array($sqlData,MYSQLI_ASSOC)){
                              echo($row['seg']);
                              }     

                        }

                        }

            ?>

Its expected to keep my values from the other columns on the same row!

This code you've shown is not responsible for resetting the row. Something else must be doing it. There is another update somewhere, possibly a trigger on the database, but it's not coming from the code sample you've posted.

Regarding your code, there are several things wrong, which others have already pointed out. I would like to add a couple more

1. Ensure you SANITIZE your data before inserting it in MySQL. Check out PDO and bindparam, for starters. Short of that, use (int) to cast the variable to an integer.
2. The update should only happen if there is new user activity.

Code:

 if ($new_user_activity['data'] == 'Seg') {
     $segHora = (int)$new_user_activity['horas'];
     $sql = ("UPDATE horario SET seg=$segHora WHERE id=1");

     if (!mysqli_query($conn, $sql)) {
         echo ("ERRO NA QUERY");
         return; // or exit, if this is not a function
     }
 }

 $showData = ("SELECT * FROM horario");
 $sqlData = mysqli_query($conn, $showData);

 while ($row = mysqli_fetch_array($sqlData, MYSQLI_ASSOC)) {
     echo ($row['seg']);
 }

It appears that the table is resetting all of the values in every column at each query. This might meant that every time you run your code, the database connection that you have set up first updates every column with zeros, and then inserts your new data. I would check your connection script.