Very Computer

you should never rely on fields with customer input.
My approach to this is that every table has an ID field as the first field.
I use a separate table to supply my tables with ID numbers.
Then I never use Master/Detail relationships but always use Filtering of the
items table. Thereby you can use whatever index you want.
I have MasterTableID field in MasterTable and DetailTableID field in
DetailTable. Then I have a MyMasterTableID  in DetailTable to be able to
filter on the items with the same MasterTableID, which is your 'invoice
header'.
Then your DBGrid will show only the item records belonging to the header
record, all sorted by your index field. (Your index could be the 'line
number field')
No unique keys, no trouble :-)

I use dBase tables, which are very suitable for indexes and compound
indexes. They don't require a unique key unless you tell it to.
If Paradox don't do what you want, use dBase tables instead. They are built
in too.

:)
Kai Inge

Quote:> have tried introducing another field called say LineNo to give the table a

Quote:> unique multi field index but in my application I need to allow the user to
> insert lines at will.  There lies the problem.  I have had a lot of

Why insert?
The normal way of doing it is simply to add the new lines at the bottom.

Try using a key field in your detail table that has no relevance to the
master-detail link.
For example
Invoice table has the following fields, Invoice Number, Date, etc, etc
Line item table has the following fields, Line ID, Sort Order, Invoice
Number, Description, etc, etc
Line ID is the key field, which can be an autoinc or similar. Use a
secondary index on Invoice Number AND Sort Order to join the two tables and
the user never has to see the key field. Because the index contains Sort
Order, the user can choose in what order the records are displayed.

I hope this helps
Cheers,
Mark Gibson

Quote:> Why insert?
> The user wishes to insert so they have control over the sequence in which
> the records are displayed and printed.