对于每个查询，您要两次调用mysqli_query.

You're calling mysqli_query twice for each query.

第二次调用它实际上是在传递资源作为查询参数，这会导致您得到错误.

The second time you call it you're actually passing a resource as the query parameter, which causes the error you're getting.

尝试将您的代码更改为此:

Try changing your code to this:

<?php
    $con=mysqli_connect("localhost","root","MYPASS","repair");
    $ID = $_REQUEST['ID'];
    $sql = "DELETE FROM tblreparation WHERE ID = {$ID}";
    if (!mysqli_query($con,$sql)) {
      die('Error: ' . mysqli_error($con));
    }
    $sql = "DELETE FROM tblrepstat WHERE repID = {$ID}";
    if (!mysqli_query($con,$sql)) {
      die('Error2: ' . mysqli_error($con));
    }
    echo "1 record deleted";
    mysqli_close($con); 
?>