mysql子查询必须加上别名，否则无法执行。如题，执行以下sql：

<select id="getUser" parameterType="map"resultType="dd.client.model.Users">SELECT * FROM(SELECTa.ID AS ID,a.CUSTOMER_ID AS CUSTOMER_ID,a.ACCOUNT AS ACCOUNT,a.PASSWORD AS PASSWORD,a.NAME AS NAME,a.SERVICE_END_TIME AS SERVICE_END_TIME,a.LAST_LOGIN_TIME AS LAST_LOGIN_TIME,a.LOGIN_FAIL_TIMES AS LOGIN_FAIL_TIMES,a.IS_ENABLE AS IS_ENABLE,a.ISDEL AS ISDEL,a.CREATE_TIME AS CREATE_TIME,a.CREATE_ID AS CREATE_ID,a.UPDATE_TIME AS UPDATE_TIME,a.UPDATE_ID AS UPDATE_ID,a.MOBILE AS MOBILE,a.EMAIL AS EMAIL,a.SEND_MOBILE AS SEND_MOBILE,a.SEND_EMAIL AS SEND_EMAIL,a.IS_LIMITED AS IS_LIMITED,a.LMT_IP AS LMT_IP,a.LMT_START_TIME AS LMT_START_TIME,a.LMT_END_TIME AS LMT_END_TIME,a.LMT_WEEK_TIME AS LMT_WEEK_TIME,a.IS_CUSTOMERGROUP AS IS_CUSTOMERGROUP,a.IS_ADMIN AS IS_ADMIN,IFNULL(b.CUSTOMER_NAME,'0') AS customer_name <!-- b.SYSTEM_NAME -->FROM users a LEFT JOIN customer b ON a.CUSTOMER_ID = b.ID) AS v_usersWHERE CUSTOMER_NAME = #{customerName}AND ACCOUNT = #{userName}</select>

时，AS v_users 是必须的，即使外层查询没有用到，也必须给子查询起一个别名，否则无法执行。