在用数据填充表之前还是在数据到位之后创建索引更好?

I have a table of about 100M rows that I am going to copy to alter, adding an index. I'm not so concerned with the time it takes to create the new table, but will the created index be more efficient if I alter the table before inserting any data or insert the data first and then add the index?I have a table of about 100M rows that I am goi