feat:优化mysqlCli

 <?php
+
 namespace Jiaoyin;
 
 use Swoole\Database\MysqliConfig;
@@ -16,7 +17,7 @@ class MysqlCli
     private     $connectConfig     = null;
     private     $database          = null;
 
-    public function __construct($host,$port,$database,$username,$password,$charset='utf8',$prefix='', $connectCount = 20)
+    public function __construct($host, $port, $database, $username, $password, $charset = 'utf8', $prefix = '', $connectCount = 20)
     {
         $this->database      = $database;
         $this->prefix        = $prefix;
@@ -35,7 +36,7 @@ class MysqlCli
 
     private function poolConnect()
     {
-        if($this->pool){
+        if ($this->pool) {
             $this->pool->close();
         }
         $this->pool   = new MysqliPool((new MysqliConfig)
@@ -45,7 +46,7 @@ class MysqlCli
             ->withCharset($this->connectConfig['charset'])
             ->withUsername($this->connectConfig['username'])
             ->withPassword($this->connectConfig['password'])
-            ,$this->connectConfig['connectCount']
+            , $this->connectConfig['connectCount']
         );
         $this->prefix = $this->connectConfig['prefix'];
     }
@@ -116,7 +117,7 @@ class MysqlCli
         $data    = $this->execute('SELECT', $sql);
         $newData = [];
         if (empty($col)) {
-            $newsql  = 'SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = "'.$this->database.'" AND TABLE_NAME="' . $this->parseTable($table) . '" ORDER BY `ORDINAL_POSITION` ASC';
+            $newsql  = 'SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = "' . $this->database . '" AND TABLE_NAME="' . $this->parseTable($table) . '" ORDER BY `ORDINAL_POSITION` ASC';
             $coldata = $this->execute('SELECT', $newsql);
             if (!$coldata) {
                 return false;
@@ -208,8 +209,12 @@ class MysqlCli
                     return false;
                 }
                 $value[1] = $this->transferValue($value[1]);
-                $symbol   = isset($value[2]) ? $value[2] : '=';
+                if ($value[1] === 'NULL') {
+                    $tmp = $value[0] . ' is NULL';
+                } else {
+                    $symbol = $value[2] ?? '=';
                     $tmp    .= $value[0] . ' ' . $symbol . ' ' . $value[1];
+                }
                 $tmp .= $key < count($where) - 1 ? ' and ' : '';
             }
             $whereTxt .= $tmp;