diff --git a/extdbms/lib/Controllers/DBMS/ServerController.php b/extdbms/lib/Controllers/DBMS/ServerController.php
index 0242261..f8577ba 100644
--- a/extdbms/lib/Controllers/DBMS/ServerController.php
+++ b/extdbms/lib/Controllers/DBMS/ServerController.php
@@ -19,32 +19,4 @@ class ServerController extends DBMSController
         }
         return $this->_serverService;
     }
-    //가용장비 현황 server_use.php
-    //CLI 접속방법 : php index.php site/server/use
-    //WEB 접속방법 : http://localhost site/server/use
-    private function setMode(GearlistEntity $entity): GearlistEntity
-    {
-        $lineup_explode = explode('.', $entity->getSpec());
-        $spec           = $lineup_explode[0];
-        $cpu            = $entity->getCPUName();
-        $entity->all = $this->getServerService()->getCountByMode("all", $cpu, $spec);
-        $entity->use = $this->getServerService()->getCountByMode("use", $cpu, $spec);
-        $entity->empty = $this->getServerService()->getCountByMode("empty", $cpu, $spec);
-        $entity->format = $this->getServerService()->getCountByMode("format", $cpu, $spec);
-        return $entity;
-    }
-    public function index(array $params): string
-    {
-        $gearlistEntities = $this->getGearlistService()->getEntitiesForLineUp();
-        //DB에 넣지않는 이유가 뭘까? DB에 넣으면 관리가 힘들어서?
-        $gearlistEntities[] = new GearlistEntity(['process' => "INTEL i5(구세대)", 'spec' => "i5-2.xx", "cpuname" => "i5-2", 'price' => "23"]);
-        $gearlistEntities[] = new GearlistEntity(['process' => "INTEL i7(구세대)", 'spec' => "i7-2.xx", "cpuname" => "i7-2", 'price' => "45"]);
-        $gearlistEntities[] = new GearlistEntity(['process' => "INTEL i7(4세대)", 'spec' => "i7-4.xx", "cpuname" => "i7-4", 'price' => "45"]);
-        $entities = [];
-        foreach ($gearlistEntities as $idx => $gearlistEntity) {
-            $entities[] = $this->setMode($gearlistEntity);
-        }
-        $this->entities = $entities;
-        return $this->render(__FUNCTION__);
-    }
 } //Class
diff --git a/extdbms/lib/Database/QueryBuilder.php b/extdbms/lib/Database/QueryBuilder.php
index 74e6743..41d9924 100644
--- a/extdbms/lib/Database/QueryBuilder.php
+++ b/extdbms/lib/Database/QueryBuilder.php
@@ -297,29 +297,36 @@ class QueryBuilder
   }
 
   //CUD부분
-  final public function insert(array $data): bool
+  final public function insert(array $data): bool|int
   {
     $columns = [];
     $placeholders = [];
+    $this->bindings = [];
+
     foreach ($data as $col => $val) {
+      $safePlaceholder = ':i_' . count($this->bindings);
       if ($val === null) {
-        // $val이 null이면 $col을 그대로 SQL로 사용
-        $columns[] = ''; // placeholder로 인해 생략
-        $placeholders[] = $col; // 예: col2=(SELECT something)
+        // null 값인 경우 SQL 조각으로 처리
+        $placeholders[] = $col;
       } else {
-        $safePlaceholder = ':i_' . preg_replace('/\W+/', '_', $col); // 안전한 바인딩 키
         $columns[] = $col;
         $placeholders[] = $safePlaceholder;
         $this->bindings[$safePlaceholder] = $val;
       }
     }
-    $sql = "INSERT INTO {$this->table} (" . implode(', ', array_filter($columns)) . ") "
-      . "VALUES (" . implode(', ', $placeholders) . ")";
+
+    $columnsSql = $columns ? '(' . implode(', ', $columns) . ')' : '';
+    $placeholdersSql = '(' . implode(', ', $placeholders) . ')';
+
+    $sql = "INSERT INTO {$this->table} {$columnsSql} VALUES {$placeholdersSql}";
+
     $stmt = $this->pdo->prepare($sql);
-    foreach ($this->bindings as $k => $v) {
-      $stmt->bindValue($k, $v);
+    foreach ($this->bindings as $key => $value) {
+      $stmt->bindValue($key, $value);
     }
-    return $stmt->execute() && $stmt->rowCount() > 0 ? (int)$this->pdo->lastInsertId() : false;
+
+    $result = $stmt->execute();
+    return $result && $stmt->rowCount() > 0 ? (int)$this->pdo->lastInsertId() : false;
   }
 
   final public function update(array $data): bool
@@ -327,6 +334,7 @@ class QueryBuilder
     if (empty($this->where)) {
       throw new \Exception(__FUNCTION__ . " 구문은 WHERE절 없이 사용할수 없습니다.");
     }
+
     $setParts = [];
     foreach ($data as $col => $val) {
       if ($val === null) {
@@ -338,8 +346,10 @@ class QueryBuilder
         $this->bindings[$placeholder] = $val;
       }
     }
+
     $sql = "UPDATE {$this->table} SET " . implode(', ', $setParts)
-      . " WHERE " . implode(' AND ', $this->where);
+      . " WHERE " . $this->buildWhereSql(); // <<< 수정된 부분
+
     $stmt = $this->pdo->prepare($sql);
     foreach ($this->bindings as $k => $v) {
       $stmt->bindValue($k, $v);
@@ -350,13 +360,16 @@ class QueryBuilder
   final public function delete(): bool
   {
     if (empty($this->where)) {
-      throw new \Exception(__FUNCTION__ . " 구문은 WHERE절 없이 사용할수 없습니다.");
+      throw new \Exception("DELETE 문에는 WHERE 절이 반드시 필요합니다.");
     }
-    $sql = "DELETE FROM {$this->table} WHERE " . implode(' AND ', $this->where);
+
+    $sql = "DELETE FROM {$this->table} WHERE " . $this->buildWhereSql();
+
     $stmt = $this->pdo->prepare($sql);
-    foreach ($this->bindings as $k => $v) {
-      $stmt->bindValue($k, $v);
+    foreach ($this->bindings as $key => $value) {
+      $stmt->bindValue($key, $value);
     }
+
     return $stmt->execute();
   }