I am facing the following situation:

I import an Excel-Sheet, then some columns are modified (e.g. "comments")
After a while, I would receive an updated Excel-Sheet containing the records from the old Excel-sheet as well as new ones.
I do not want to import the records that already exist in the database.

Step-by-Step:

Initial Excel-sheet

```
col1  col2  comments
A        A       
A        B

```

After import, some fields will get manipulated

```
col1  col2       comments
A        A       looks good
A        B       fine with me

```

Then I receive an excel sheet with updates

```
col1  col2  comments
A        A       
A        B
A        C

```

After this update-step, the database should look like 

```
col1  col2       comments
A        A       looks good
A        B       fine with me
A        C

```

I was planning to simply create a unique index on all fields that won't get manipulated, so only the new records will get imported. (sth like 

```
ALTER TABLE tbl ADD CONSRAINT unique_key UNIQUE (col1,col2)

```

My problem now is that Access somehow only allows composite indices of max. 10 fields. My tables all have around 11-20 cols...

I could maybe import the updated xls to a temp. table, and do s.th like

```
INSERT INTO tbl_old SELECT col1,col2, "" FROM tbl_new WHERE (col1,col2) NOT IN (SELECT col1,col2 FROM tbl_old UNION SELECT col1,col2 FROM tbl_new)

```

But I'm wondering if there isn't a more straigt-forward way...

Any ideas how I can solve that?