为什么这句SQL出错解决思路

为什么这句SQL出错
exec( 'update   xsyjtotalyku_1_admin   set   ysbl=ltrim(rtrim(cast(cast(100*ysje/xsje   as   decimal(18,2))   as   char(10)))) '+ ' '% ' ')

------解决方案--------------------
exec( 'update xsyjtotalyku_1_admin set ysbl=ltrim(rtrim(cast(cast(100*ysje/xsje as decimal(18,2)) as char(10))))+ ' '% ' ' ')