MyBatis中关于SQL标签的用法（重用SQL 代码段）

<select id="findById" resultType="cn.tedu.mybatis.entity.User">
        SELECT
         id,username,password,age,phone,email
        FROM t_user
        WHERE
        id=#{id}
    </select>

<sql id="userColumns"> id,username,password,age,phone,email</sql>
    <select id="findById" resultType="cn.tedu.mybatis.entity.User">
        SELECT
         <include refid="userColumns"></include>
        FROM t_user
        WHERE
        id=#{id}
    </select>