Sequential Number in Access Form Based on Field Selection - ms-access

Question

Hoping someone can assist here, I'm fairly new to SQL but yet the most experienced person in the office so this job has fallen to me.
I'm trying to build a form that will insert customer orders into production scheduling. The form allows users to select a machine from the machine list table, however what I need it to do after that is find the last job number for that specific machine and show the next sequential number in a text box; and that's where I'm stuck. The goal is that when the production user is adding an order to the database, by selecting their machine the next available job number is automatically populated. The information entered will be saved to a master scheduling table.
I've got a query built that pulls the entire list of machine and job combinations, as my goal was to build a macro that could search from that list, but so far I haven't gained any traction. Any help/advice would be appreciated!

Answer 1

Welcome to SO.
My suggestion would be to create a table to hold the sequence numbers. For the sake of this example, let's call it ProdSeq, which means Production Sequences. As part of this table definition, I would use Data Macros (Access 2010 and up) in order to assign the sequences as records are added. I would use a Unique index in order to ensure no duplicates are created.
Table: ProdSeq (Field Definitions)
MachineID (Number - Long) - References Machine ID in Machines Table
ProdSeq (Number - Long) - Incremented for each machine
OrderID (Number - Long) - References Order ID in Orders Table
Indexes
Under the Design ribbon tab when designing the ProdSeq table, click the Indexes button.
Create an Index called UniqueKey
Row 1: Index Name = UniqueKey, Field Name = MachineID
Row 2: Index Name = Leave Blank, Field Name = ProdSequence
Click on Row 1, Column 1 and set the following Index Properties:
Primary = Yes
Unique = Yes
Ignore Nulls = No
Data Macros
Under the Design ribbon tab when designing the ProdSeq table, click the Create Data Macros button, and then the Before Change button. Enter the following data macro: (Pastebin link)
Create the Before Change data macro and set it as follows:
If [IsInsert] Then
SetLocalVar
Name LatestProdSequence
Expression = 0
Look Up A Record In ProdSeq
Where Condition =[ProdSeqLookup].[MachineID]=[ProdSeq].[MachineID] And
[ProdSeqLookup].[LatestSeq] = True
Alias ProdSeqLookup
SetLocalVar
Name LatestProdSequence
Expression =[ProdSeqLookup].[ProdSequence]
SetField
Name ProdSeq.ProdSequence
Value = [LatestProdSequence]+1
SetField
Name ProdSeq.LatestSeq
Value = True
End If
Pay special attention to the fact that only one SetLocalVar is within the LookUpRecord clause. Use the collapse / expand (-/+) button on LookUpRecord to make sure.
Create the After Insert data macro and set it as follows: (Pastebin Link)
For Each Record In ProdSeq
Where Condition = [ProdSeqFlagFix].[MachineID]=[ProdSeq].[MachineID] And
[ProdSeqFlagFix].[LatestSeq]=True And
[ProdSeqFlagFix].[ProdSequence]<>[ProdSeq].[ProdSequence]
EditRecord
SetField
Name ProdSeqFlagFix.LatestSeq
Value = False
End EditRecord
Test it Out
You can create this in a blank database in order to see what I am talking about. You should be able to adapt it to your specific situation.
Form
On your form, when the user selects a machine and order, you can use VBA in order to check for an existing record in ProdSeq, and fetch the ID. If no record exists, then you can create one, and then return the ProdSeq ID to the form.
Note: Depending on your design, you may also need to create a Data Macro on the Schedules table. Suppose someone creates a schedule with a specific machine and order and reserves a production slot. Now assume they change the Order ID .. we have a production slot reserved in error. So if this applies, you'll also need an AfterUpdate data macro on the Scheduling table that checks to see if [old].OrderID <> [Schedule].OrderID - and if they do differ, to remove the Production slot from the schedule table and the Prod Sequence table.

Answer 2

As I understand, you need to add suggested value for job number when you add new record to the table. If so, you can use, for instance DMax function. Here is example of VBA code for this, it can be called when you add new record:
Me.MyTextBox = DMax("JobField", "JobsTable") + 1
I supposed that JobField, which contains job numbers has Number data type.
Also you can use this function inside any query as a calculated field.