diff --git a/src/main/resources/vm/xml/mapper.xml.vm b/src/main/resources/vm/xml/mapper.xml.vm
index 442c19a..160abf6 100644
--- a/src/main/resources/vm/xml/mapper.xml.vm
+++ b/src/main/resources/vm/xml/mapper.xml.vm
@@ -73,12 +73,12 @@ PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
         insert into ${tableName}
         <trim prefix="(" suffix=")" suffixOverrides=",">
 #foreach($column in $columns)
-            <if test="$column.javaField != null #if($column.javaType == 'String' ) and $column.javaField != ''#end">$column.columnName,</if>
+            <if test="$column.javaField != null#if($column.javaType == 'String' && $column.required) and $column.javaField != ''#end">$column.columnName,</if>
 #end
          </trim>
         <trim prefix="values (" suffix=")" suffixOverrides=",">
 #foreach($column in $columns)
-            <if test="$column.javaField != null #if($column.javaType == 'String' ) and $column.javaField != ''#end">#{$column.javaField},</if>
+            <if test="$column.javaField != null#if($column.javaType == 'String' && $column.required) and $column.javaField != ''#end">#{$column.javaField},</if>
 #end
          </trim>
     </insert>
@@ -88,7 +88,7 @@ PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
         <trim prefix="SET" suffixOverrides=",">
 #foreach($column in $columns)
 #if($column.columnName != $pkColumn.columnName)
-            <if test="$column.javaField != null #if($column.javaType == 'String' ) and $column.javaField != ''#end">$column.columnName = #{$column.javaField},</if>
+            <if test="$column.javaField != null#if($column.javaType == 'String' && $column.required) and $column.javaField != ''#end">$column.columnName = #{$column.javaField},</if>
 #end
 #end
         </trim>