[php] need to test if sql query was successful

I have this query and if it returns successful, I want another function to process, if not, do not process that function.

Here is the code for running the query

global $DB;
$DB->query("UPDATE exp_members SET group_id = '$group_id' WHERE member_id = '$member_id'");

I imagine it is something like...

if($DB) { 
    //success 
} else { 
    //failure 
}

global $DB;
$status = $DB->query("UPDATE exp_members SET group_id = '$group_id' WHERE member_id = '$member_id'");

if($status == false)
{ 
    die("Didn't Update"); 
}

If you are using mysql_query in the backend (whatever $DB->query() uses to query the database), it will return a TRUE or FALSE for INSERT, UPDATE, and DELETE (and a few others), commands, based on their status.

mysql_affected_rows

I understand that by saying "successful" you want to know if any rows have been updated. You can check it with this function.

If you use PDO -> http://www.php.net/manual/en/pdostatement.rowcount.php

if you're not using the -> format, you can do this:

$a = "SQL command...";
if ($b = mysqli_query($con,$a)) {
  // results was successful
} else {
  // result was not successful
}

if ($DB->rowCount() > 0)
   {/* Update worked because query affected X amount of rows. */}
else
    {$error = $DB->errorInfo();}

if the value is 0 then it wasn't successful, but if 1 then successful.

$this->db->affected_rows();

if ($DB->query(...)) { success }
else { failure }

query should return false on failure (if you're using mysql_query or $mysqli->query). If you want to test if the UPDATE query actually did anything (which is a totally different thing than "successful") then use mysql_affected_rows or $mysqli->affected_rows

Check this:

<?php
if (mysqli_num_rows(mysqli_query($con, sqlselectquery)) > 0)
{
    echo "found";
}
else
{
    echo "not found";
}
?>

<!----comment ---for select query to know row matching the condition are fetched or not--->

mysqli_affected_rows returns number of items affected.

This has proven the safest mechanism for me to test for failure on insert or update:

$result = $db->query(' ... ');
if ((gettype($result) == "object" && $result->num_rows == 0) || !$result) {
   failure 
}

You can use this to check if there are any results ($result) from a query:

if (mysqli_num_rows($result) != 0)
 {
  //results found
 } else {
  // results not found
 }