我把四个excel 表格导入到SAS里面，然后将他们合并成一个表格，但是合并时出现错误，提示：
ERROR: Variable MIN has been defined as both character and numeric.
ERROR: Variable TRANS_T has been defined as both character and numeric.
ERROR: Variable START_T has been defined as both character and numeric.
ERROR: Variable FINISH_T has been defined as both character and numeric
请教，如何将这些变量的格式改成一样呢？
非常感谢！