Detail Sort Field in a Master Detail Report

Question

Hello,
New Apex user here. I am working with version 4.0.2.00.07. I have created a Master Detail form, and everything is working perfectly. I have one additional requirement for which I can't seem to find a good method of implementation. The detail table contains a field which I need to use for sequencing the detail records in a specific order for a given master record (this field is not the primary key). Let's say the table field is called det_seq. My question is, what is the best way to have the next incremented number added to a new record when the user clicks the "Add Row" button in the detail region? So, for instance, if there are 5 existing detail records, I want the next record added with the "Add Row" button to default the number 6 into the det_seq field. Another desirable, but not absolutely necessary, feature would be to give the end user the ability to re-order the detail records, updating the det_seq field as they do so. Any guidance would be greatly appreciated.
Thanks!
Mike

Answer 1

Hi Mike - welcome to ApEx!
Could more than one user add detail rows to the same master row at one time? If so, incrementing det_seq on a click of the "Add Row" button could create duplicate det_seq values:
User A clicks "Add Row" getting det_seq 1, and begins to enter data (doesn't yet save).
User B clicks "Add Row" on the same master record, getting det_seq 1, and begins to enter data.
User A saves, no problem.
User B saves, another det_seq = 1 is saved (or an exception is thrown if you've declared det_seq to be unique within a master).
If that could be an issue for you, one thing to consider is assigning the det_seq value from within a before-insert trigger so that:
User A clicks "Add Row" (det_seq is null), and begins to enter data.
User B clicks "Add Row" (det_seq is null), and begins to enter data.
User A saves, the before-insert trigger fires assigning 1 to det_seq.
User B saves, the before-insert trigger fires assigning 2 to det_seq.
As far as actually getting the next value for det_seq within a given master, here's one way (assume that :MASTER_ID is an item on the master-detail form that is holding the primary key of the master table, and that your child table also has this as a foreign key back to the master table):
SELECT NVL(MAX(det_seq), 0) + 1
  INTO l_next_det_seq
  FROM detail_table
WHERE master_id = :MASTER_IDThe NVL takes care of the case where there are not yet any detail rows (meaning that MAX would return NULL).
On the re-ordering feature - I can't give a lot of detail without trying it out for myself, but maybe something to look into:
- Put a couple buttons/images/links at the end of each detail row indicating "move up"/"move down".
- Create "move up"/"move down" page processes, and attach javascript to the buttons/images/links to fire them on a click.
- The page processes would update the clicked row's det_seq by swapping values with the previous row's det_seq ("move up") or next row's det_seq ("move down"). The special cases of course are when the first det_seq is being moved up or the last det_seq is being moved down and they have to loop around - all of the rows det_seq's then have to swap. I'd love to see that when you've got it going!
Hope this helps and I hope you enjoy working with ApEx,
John
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