I used advanced filter for the first column, and I did the same for the second column.
After I verified it, I couldn't get the correct corresponding value on the second column. for example for a I have to get b in column b, but I got c from column b.
Please make sure you state the complete problem in first post. Your first post talks about only 1 column, but it looks like you actually have multiple columns. Could you post a small sample table of data so we can see what you/we are dealing with, and what you'd like to see?