MySQL - why not index every field?

Question

Recently I\'ve learned the wonder of indexes, and performance has improved dramatically. However, with all I\'ve learned, I can\'t seem to find the answer to this question.<

Answer 1

It is not a good idea to indexes all the columns in a table. While this will make the table very fast to read from, it also becomes much slower to write to. Writing to a table that has every column indexed would involve putting the new record in that table and then putting each column's information in the its own index table.