我试图用SET @rank = 0创建一个视图;在里面,但它给了我错误.尝试过不同的东西,但它没有用.谁能指点我正确的方向？

CREATE VIEW S1_Bottom_Performer_AHT as (
SET @rank=0
SELECT @rank := @rank+1 AS '#',ei.SM,ei.TM,es.Month_Date,ei.emp_id,ei.DNAME,ei.STATUS,ei.SHIFT,ei.SKILL,ei.HIRE_DATE,ifnull(TIMESTAMPDIFF(MONTH,now()),'-') AS Tenure,ifnull(es.Call_Handled,'-') AS Call_Handled,ifnull(es.AHT,'-') AS AHT
FROM mtl_extended_info ei
LEFT OUTER JOIN
  ( SELECT es.Employee_ID,sum(es.Calls_Handled_Ct) AS Call_Handled,round((sum(es.I_Talk_Time_Sec) + sum(es.Hold_Time_Sec) + sum(es.I_Work_Time_Sec) + sum(es.I_AUX_Out_Time_Sec)) / sum(es.Calls_Handled_Ct)) AS AHT
   FROM cdl_agent_call_voume_gen es
   WHERE es.Month_Date = '2013-09-01'
   GROUP BY es.Employee_ID,es.Month_Date ) es ON es.Employee_ID = ei.emp_id
WHERE es.Month_Date = '2013-09-01'
  AND ei.Visible = 1
  AND ei.SKILL != 'RSD'
GROUP BY ei.emp_id
ORDER BY es.AHT DESC LIMIT 80);

错误信息：

#1064 - You have an error in your sql Syntax; check the manual that corresponds to your MysqL server version for the right Syntax to use near 'SET @rank=0
SELECT @rank := @rank+1 AS '#',' at line 2