foreach ----$

<foreach collection="tailList" item="tail" index="index" open=" " close=" " separator=",">
    min(case 
when tail_no=' ${tail.tail_No}' and type=2 then '1' 
when tail_no=' ${tail.tail_No}' and type=3 then '2' 
else 'N/A' end) AS  ${tail.tailNo}

</foreach>

是$  不是#