在PHP中使用mysql查询返回0个结果

Question

I am trying to create a graph which takes data from one of our databases and counts the number of issues we had for each of the last 12 months. The query is running fine but it keeps returning 0 results even though there is records in the database that match the query. The code i am using is as follows...

 <?php
if (isset($_POST['dept'])) {
    $dept = $_POST['dept'];

} else {

    $dept = '';

}


for ($i = 1; $i <= 12; $i++) {
    $months[] = date("Y-m-d", strtotime(date('Y-m-01') . " -$i months"));

}

foreach ($months as $month => $value) {

    $theMonth = date("M", strtotime($value));
    $theYear  = date("Y", strtotime($value));

    $sql = "SELECT `c_ID`, `department`, `departmentSub`,  `todaysDate`, \n" . "SUM(CASE WHEN department='$dept' AND  departmentSub LIKE 'Loading Error' AND MONTH(todaysDate) = MONTH($value) AND YEAR(todaysDate) = YEAR($value) THEN 1 ELSE 0 END) AS loadingErrors,\n" . "SUM(CASE WHEN department='$dept' AND  departmentSub LIKE 'Bad Customer Service' AND MONTH(todaysDate) = MONTH($value) AND YEAR(todaysDate) = YEAR($value) THEN 1 ELSE 0 END) AS custService\n" . "FROM `nonConformance`";


    if ($result = mysqli_query($conn, $sql)) {
        // Return the number of rows in result set
        while ($row = $result->fetch_assoc()) {
            $loadingErrors = $row['loadingErrors'];
            $custService   = $row['custService'];
        }

    }
}
?>

I cant figure out why this is not returning any results, can anyone help me out with this it would be much appreciated.

Thanks!

[example data] http://imgur.com/g0UzcpR

Answer 1

In your query, you're not passing through $value as a string. Try surrounding $value with apostrophes:

 $sql = "SELECT `c_ID`, `department`, `departmentSub`,  `todaysDate`, \n" . "SUM(CASE WHEN department='$dept' AND  departmentSub LIKE 'Loading Error' AND MONTH(todaysDate) = MONTH('$value') AND YEAR(todaysDate) = YEAR('$value') THEN 1 ELSE 0 END) AS loadingErrors,\n" . "SUM(CASE WHEN department='$dept' AND  departmentSub LIKE 'Bad Customer Service' AND MONTH(todaysDate) = MONTH('$value') AND YEAR(todaysDate) = YEAR('$value') THEN 1 ELSE 0 END) AS custService\n" . "FROM `nonConformance`";

MONTH($value) becomes MONTH('$value') and YEAR($value) becomes YEAR('$value')

Also, make sure you're outputting the values of $loadingErrors and $custService within the foreach ($months as $month => $value) { loop, otherwise dates that have zero values will overwrite the previous.

Answer 2

Have you tried this in your query?

Replace

    departmentSub LIKE 'Loading Error'

with

    departmentSub = 'Loading Error'

or

    departmentSub LIKE '%Loading Error%'

If your looking for an exact string value, why use LIKE?