diff --git a/readme.md b/readme.md
index 087e475..6693f9f 100644
--- a/readme.md
+++ b/readme.md
@@ -2,7 +2,7 @@
 
 ### Configuration
 
-##### 添加文件: `BitFlagBehavior.php`
+#### 添加文件: `BitFlagBehavior.php`
 
 ```php
 <?php
@@ -74,11 +74,11 @@ class BitFlagBehavior extends Behavior
 
     public function afterFind()
     {
-        $owner = $this->owner;
+        valuewner = $this->owner;
         foreach ($this->bitFlags as $bitFlag => $flags) {
-            $bitFlagValue = $owner->$bitFlag;
+            $bitFlagValue = valuewner->$bitFlag;
             foreach ($flags as $pos => $flag) {
-                $owner->$flag = ($bitFlagValue & 1 << $pos) >> $pos;
+                valuewner->$flag = ($bitFlagValue & 1 << $pos) >> $pos;
             }
         }
     }
@@ -90,13 +90,13 @@ class BitFlagBehavior extends Behavior
      */
     public function setBitFlag($bitFlag, $flags)
     {
-        $owner = $this->owner;
+        valuewner = $this->owner;
         foreach ($flags as $pos => $flag) {
-            $flagValue = $owner->$flag;
+            $flagValue = valuewner->$flag;
             if ($flagValue === null) {
                 continue;
             }
-            $owner->$bitFlag = $this->getBitFlagUpdate($owner->$bitFlag, $pos, $flagValue);
+            valuewner->$bitFlag = $this->getBitFlagUpdate(valuewner->$bitFlag, $pos, $flagValue);
         }
     }
 
@@ -120,38 +120,38 @@ class BitFlagBehavior extends Behavior
     /**
      * {@inheritdoc}
      */
-    public function __get($name)
+    public function __get(name)
     {
-        return $this->_attributes[$name];
+        return $this->_attributes[name];
     }
 
     /**
      * {@inheritdoc}
      */
-    public function __set($name, $value)
+    public function __set(name, $value)
     {
-        $this->_attributes[$name] = $value;
+        $this->_attributes[name] = $value;
     }
 
     /**
      * {@inheritdoc}
      */
-    public function canGetProperty($name, $checkVars = true)
+    public function canGetProperty(name, $checkVars = true)
     {
-        return parent::canGetProperty($name, $checkVars) || ArrayHelper::keyExists($name, $this->_attributes);
+        return parent::canGetProperty(name, $checkVars) || ArrayHelper::keyExists(name, $this->_attributes);
     }
 
     /**
      * {@inheritdoc}
      */
-    public function canSetProperty($name, $checkVars = true)
+    public function canSetProperty(name, $checkVars = true)
     {
-        return parent::canSetProperty($name, $checkVars) || ArrayHelper::keyExists($name, $this->_attributes);
+        return parent::canSetProperty(name, $checkVars) || ArrayHelper::keyExists(name, $this->_attributes);
     }
 }
 ```
 
-##### 在需要的`Model`里添加`Behavior`
+#### 在需要的`Model`里添加`Behavior`
 ```php
 <?php
 
@@ -219,7 +219,7 @@ class MyModel extends base\MyModel
 }
 ```
 
-##### 添加文件 `MyModelQuery`
+#### 添加文件 `MyModelQuery`
 
 ```php
 <?php
@@ -285,11 +285,156 @@ class MyModelQuery extends ActiveQuery
 
 ### Usage
 
-##### Search
+#### Search
 
 ```php
 $myModels = MyModel::find()
             ->andWhereBitFlags(['s0' => 1, 's1' => 0])
             ->orWhereBitFlags(['s2' => 0, 's3' => 1])
             ->all();
+```
+
+#### Migration
+
+##### 从最高位添加标志位，默认值为 `1`  (默认值为 `0` 无操作)
+
+添加公式： `value + (1 << n)`
+删除公式： `value - (1 << n)`
+
+migration:
+```php
+<?php
+
+use yii\db\Migration;
+
+/**
+ * Class mxxxxxx_xxxxxx_update_{table}_table_{column}_column
+ */
+class mxxxxxx_xxxxxx_update_{table}_table_{column}_column extends Migration
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function safeUp()
+    {
+        $this->update('{table}', ['{column}' => new \yii\db\Expression('{column} + (1 << {n})')]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function safeDown()
+    {
+        $this->update('{table}', ['{column}' => new \yii\db\Expression('{column} - (1 << {n})')]);
+    }
+}
+```
+
+##### 标志位插入到第 `n` 位，默认值为 `k`
+
+插入公式： `(value >> n << (n + 1)) + (value & ((1 << n) - 1)) + (k << n)`
+删除公式： `(value >> (n + 1) << n) + (value & ((1 << n) - 1))`
+
+migration:
+```php
+<?php
+
+use yii\db\Migration;
+
+/**
+ * Class mxxxxxx_xxxxxx_update_{table}_table_{column}_column
+ */
+class mxxxxxx_xxxxxx_update_{table}_table_{column}_column extends Migration
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function safeUp()
+    {
+        $this->update('{table}', ['{column}' => new \yii\db\Expression('({column} >> {n} << ({n} + 1)) + ({column} & ((1 << {n}) - 1)) + ({k} << {n})')]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function safeDown()
+    {
+        $this->update('{table}', ['{column}' => new \yii\db\Expression('({column} >> ({n} + 1) << {n}) + ({column} & ((1 << {n}) - 1))')]);
+    }
+}
+```
+
+封装：
+
+```php
+/**
+ * @param string $column
+ * @param int $pos
+ * @param string $operate
+ * @param int $defaultValue
+ * @return \yii\db\Expression
+ */
+public function getBitFlagExpression($column, $pos, $operate, $defaultValue = 0)
+{
+    if ($operate == 'insert') {
+        $expresstion = "($column >> $pos << ($pos + 1)) + ($column & ((1 << $pos) - 1)) + ($defaultValue << $pos)";
+    } elseif ($operate == 'delete') {
+        $expresstion = "($column >> ($pos + 1) << $pos) + ($column & ((1 << $pos) - 1))";
+    } else {
+        throw new \InvalidArgumentException('$operate: '.$operate);
+    }
+
+    return new \yii\db\Expression($expresstion); 
+}
+```
+
+migration:
+
+```php
+<?php
+
+use yii\db\Migration;
+
+/**
+ * Class mxxxxxx_xxxxxx_update_{table}_table_{column}_column
+ */
+class mxxxxxx_xxxxxx_update_{table}_table_{column}_column extends Migration
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function safeUp()
+    {
+        $this->update('{table}', ['{column}' => $this->getBitFlagExpression('{column}', 1, 'insert', {k})]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function safeDown()
+    {
+        $this->update('{table}', ['{column}' => $this->getBitFlagExpression('{column}', 1, 'delete')]);
+    }
+
+    /**
+     * @param string $column
+     * @param int $pos
+     * @param string $operate
+     * @param int $defaultValue
+     * @return \yii\db\Expression
+     */
+    public function getBitFlagExpression($column, $pos, $operate, $defaultValue = 0)
+    {
+        if ($operate == 'insert') {
+            $expresstion = "($column >> $pos << ($pos + 1)) + ($column & ((1 << $pos) - 1)) + ($defaultValue << $pos)";
+        } elseif ($operate == 'delete') {
+            $expresstion = "($column >> ($pos + 1) << $pos) + ($column & ((1 << $pos) - 1))";
+        } else {
+            throw new \InvalidArgumentException('$operate: '.$operate);
+        }
+
+        return new \yii\db\Expression($expresstion); 
+    }
+}
+
 ```
\ No newline at end of file