MyBatis 3 自动生成 主键 针对不同的数据库（oracle/sqlserver/mysql）

<insert id="saveUserInfo" parameterType="UserInfo">
        <selectKey resultType="int"  keyProperty="userId" order="BEFORE">   
            <![CDATA[SELECT SEQ_COMMON.NEXTVAL AS ID FROM DUAL]]>   
          </selectKey>
        <![CDATA[insert into userinfo(userId,userName,phone,age,birthday,remark) 
        values(#{userId},#{userName},#{phone},#{age},#{birthday},#{remark})]]>
    </insert>

<insert id="saveUserInfo" parameterType="UserInfo"  useGeneratedKeys="true"   keyProperty="id">
        insert into
        userinfo(userName,phone,age,birthday,remark)
        values(#{userName},#{phone},#{age},#{birthday},#{remark})  
   </insert>

<!-- Microsoft SQL Server IDENTITY Column 改进-->   
<insertid="insertProduct-MS-SQL"parameterClass="com.domain.Product">   
    <selectKeyresultClass="int"keyProperty="id">   
        <![CDATA[insert into PRODUCT (PRD_DESCRIPTION) values(#description#)
         SELECT SCOPE_IDENTITY() AS ID ]]>  
    </selectKey>   
</insert>