如果行已存在则更新表，如果数据集中不存在行，则插入时更新表

I am creating a stored procedure where I am inserting into a table from a SELECT statement. The table has 4 columns (e.g. Col1, Col2, Col3, Col4). Column1 has a unique value. and Column4 is the timestamp of when the rows are inserted.I am creating a stored procedure where I am ins