datamining problem: varchar mistake

create mining model DecisionTree_LevelPredict
(	
	stu_ID varchar(50) key,
	stu_gender varchar(50) discrete,
	stu_birthyear varchar(50) discrete,
	stu_education varchar(50) discrete,
	stu_levels varchar(50) predict
)
using Microsoft_Desicion_Trees (Complexity_Penalty=0.5)

insert into DecisionTree_LevelPredict
(stu_ID,stu_gender,stu_birthyear,stu_education,stu_levels)
openrowset ('Microsoft.Jet.OLEDB.4.0','Data Source=dbo.customer;','select ID,gender,birthyear,education,levels')
select * from DecisionTree_LevelPredict