diff --git a/public/include/classes/block.class.php b/public/include/classes/block.class.php
index b65d88a3..5f1668bd 100644
--- a/public/include/classes/block.class.php
+++ b/public/include/classes/block.class.php
@@ -145,7 +145,7 @@ class Block extends Base {
    * @return bool
    **/
   public function setConfirmations($block_id, $confirmations) {
-    $stmt = $this->mysqli->prepare("UPDATE $this->table SET confirmations = ? WHERE id = ?");
+    $stmt = $this->mysqli->prepare("UPDATE $this->table SET confirmations = ? WHERE id = ? LIMIT 1");
     if ($this->checkStmt($stmt) && $stmt->bind_param("ii", $confirmations, $block_id) && $stmt->execute())
       return true;
     return $this->sqlError();
diff --git a/public/include/classes/payout.class.php b/public/include/classes/payout.class.php
index ce4368e8..a83d87e2 100644
--- a/public/include/classes/payout.class.php
+++ b/public/include/classes/payout.class.php
@@ -60,7 +60,7 @@ class Payout Extends Base {
    * @return boolean bool True or False
    **/
   public function setProcessed($id) {
-    $stmt = $this->mysqli->prepare("UPDATE $this->table SET completed = 1 WHERE id = ?");
+    $stmt = $this->mysqli->prepare("UPDATE $this->table SET completed = 1 WHERE id = ? LIMIT 1");
     if ($stmt && $stmt->bind_param('i', $id) && $stmt->execute())
       return true;
     return $this->sqlError('E0051');
diff --git a/public/include/classes/share.class.php b/public/include/classes/share.class.php
index d0fd0144..42242632 100644
--- a/public/include/classes/share.class.php
+++ b/public/include/classes/share.class.php
@@ -244,7 +244,7 @@ class Share Extends Base {
     while ($affected > 0) {
       // Sleep first to allow any IO to cleanup
       sleep($this->config['purge']['sleep']);
-      $stmt = $this->mysqli->prepare("DELETE FROM $this->table WHERE id > ? AND id <= ? LIMIT " . $this->config['purge']['shares']);
+      $stmt = $this->mysqli->prepare("DELETE FROM $this->table WHERE id > ? AND id <= ? ORDER BY id LIMIT " . $this->config['purge']['shares']);
       $start = microtime(true);
       if ($this->checkStmt($stmt) && $stmt->bind_param('ii', $previous_upstream, $current_upstream) && $stmt->execute()) {
         $affected = $stmt->affected_rows;
diff --git a/public/include/classes/statistics.class.php b/public/include/classes/statistics.class.php
index 5ae10690..4b369931 100644
--- a/public/include/classes/statistics.class.php
+++ b/public/include/classes/statistics.class.php
@@ -567,7 +567,7 @@ class Statistics extends Base {
    * @param worker_id int Worker ID to fetch hashrate for
    * @return data int Current hashrate in khash/s
    **/
-  public function getWorkerHashrate($worker_id) {
+  public function getWorkerHashrate($worker_id,$interval=600) {
     $this->debug->append("STA " . __METHOD__, 4);
     if ($data = $this->memcache->get(__FUNCTION__ . $worker_id)) return $data;
     $stmt = $this->mysqli->prepare("
@@ -576,7 +576,7 @@ class Statistics extends Base {
            " . $this->user->getTableName() . " AS u
       WHERE u.username = SUBSTRING_INDEX( s.username, '.', 1 )
         AND our_result = 'Y'
-        AND s.time > DATE_SUB(now(), INTERVAL 600 SECOND)
+        AND s.time > DATE_SUB(now(), INTERVAL ? SECOND)
         AND u.id = ?");
     if ($this->checkStmt($stmt) && $stmt->bind_param("i", $account_id) && $stmt->execute() && $result = $stmt->get_result() )
       return $this->memcache->setCache(__FUNCTION__ . $worker_id, $result->fetch_object()->hashrate);
diff --git a/public/include/classes/worker.class.php b/public/include/classes/worker.class.php
index a028d5a4..ea5d68a1 100644
--- a/public/include/classes/worker.class.php
+++ b/public/include/classes/worker.class.php
@@ -31,7 +31,7 @@ class Worker extends Base {
       }
       // Prefix the WebUser to Worker name
       $value['username'] = "$username." . $value['username'];
-      $stmt = $this->mysqli->prepare("UPDATE $this->table SET password = ?, username = ?, monitor = ? WHERE account_id = ? AND id = ?");
+      $stmt = $this->mysqli->prepare("UPDATE $this->table SET password = ?, username = ?, monitor = ? WHERE account_id = ? AND id = ? LIMIT 1");
       if ( ! ( $this->checkStmt($stmt) && $stmt->bind_param('ssiii', $value['password'], $value['username'], $value['monitor'], $account_id, $key) && $stmt->execute()) )
         $iFailed++;
       }
@@ -259,7 +259,7 @@ class Worker extends Base {
    **/
   public function deleteWorker($account_id, $id) {
     $this->debug->append("STA " . __METHOD__, 4);
-    $stmt = $this->mysqli->prepare("DELETE FROM $this->table WHERE account_id = ? AND id = ?");
+    $stmt = $this->mysqli->prepare("DELETE FROM $this->table WHERE account_id = ? AND id = ? LIMIT 1");
     if ($this->checkStmt($stmt) && $stmt->bind_param('ii', $account_id, $id) && $stmt->execute() && $stmt->affected_rows == 1)
         return true;
     return $this->sqlError('E0061');