如何将一列数据库拆分为多列，并将date-time数据类型的值与string数据类型进行比较

I have two different MS excel sheets containing 40000 rows of data having around 12 columns.I would like to import the data from both the sheets in a database(any database can be used) into 2 different tables(table_a & table_b). Now, there is column(with column name: "start_time") in 'table_a' with the datatype 'date/time' and the value stored is "08:30:50". Also, there is a column(with column name: "total_time") in 'table_b' with the datatype 'string' and the value stored is "0800-1000".I have two different MS excel sheets containing