ibatis中selectKey的作用

ibatis 插入数据将selectKey放在insert之后，通过LAST_INSERT_ID() 获得刚插入的自动增长的id的值。
mysql中：
    <selectKey resultClass="int" keyProperty="id">
             <![CDATA[SELECT LAST_INSERT_ID() AS ID]]>
    </selectKey>

例子：
<insert id="insertUser" parameterClass="ibatis.User">
          insert into user
          (name,password)
          values
          (#name#,#password#)
          <selectKey resultClass="long" keyProperty="id">  
             SELECT LAST_INSERT_ID() AS ID  
        </selectKey>  
</insert>

oracle中：

要把<selectKey resultClass="long" keyProperty="id">  
             SELECT LAST_INSERT_ID() AS ID  
        </selectKey>  放前面，因为在oracle中是先生成id

<insert id="insertUser" parameterClass="ibatis.User">

     <selectKey resultClass="long" keyProperty="id">  
            SELECT LAST_INSERT_ID() AS ID  
        </selectKey>
          insert into user
          (name,password)
          values
          (#name#,#password#)
         
</insert>