I have many large lists. Each contains unique entries, as well as duplicate
entires. I need to combine all lists into one long list with no duplicates.
Using one field as a primary key value, I want to remove all duplicate
entries. Where the data is different but the key entry is the same, I only
need to keep the first occurrence.

e.g.
List 1
key field | name | address | city
abcd | A bunch of data, some empty fields.....
efgh
zzww
qnbc

List 2
key field | name | address | City| Phone Number
kdkd | A bunch of data, some empty fields.....
abcd
werf
asdf
asdd
zzww
poio

----------------------
Note that entries abcd and zzww occur in both lists.

Aligning the columns and putting all lists into one big list is simple.
Please help me with a method to identify the duplicates and keep only the
first occurence of them, based on the key field value.

Note that these lists could have many thousands of entries and some entries
occur many times, so the simplest method would be most appreciated for the
sake of speed. For now, I am pulling the data into a full power text editor
and that includes sort and remove duplicate functions. I think I can figure
out how to do this in Excel with multiple sorts and 'if this cell is the same
as one above it' things, but I am finding it is taking many many steps to
accomplish this, specially if there are more than 2 duplicates. Is there a
simple function like the POSIX uniq command to do this, preferably in one
step?

thanks