With Access versions 2010 and later you can use an event-driven data macro to generate the sequential ID. For example, say you have a table named [poledata]. Open it in Design View and add two fields:
alternate_id_seq – Numeric (Long Integer)
alternate_id – Text(20)
Save the changes to your table and then switch to Datasheet View.
In the Access ribbon, switch to the "Table Tools > Table" tab and click "Before Change"
then enter the following macro ...
... or paste the following XML into the macro editor window
<?xml version="1.0" encoding="utf-16" standalone="no"?>
<DataMacros xmlns="http://schemas.microsoft.com/office/accessservices/2009/11/application">
<DataMacro Event="BeforeChange">
<Statements>
<ConditionalBlock>
<If>
<Condition>[IsInsert]</Condition>
<Statements>
<Action Name="SetLocalVar">
<Argument Name="Name">next_seq</Argument>
<Argument Name="Value">1</Argument>
</Action>
<Action Name="SetLocalVar">
<Argument Name="Name">prefix</Argument>
<Argument Name="Value">"SAC" & Year(Date()) Mod 100 & "-"</Argument>
</Action>
<LookUpRecord>
<Data Alias="pd">
<Query>
<References>
<Reference Source="poledata" Alias="pd" />
</References>
<Results>
<Property Source="pd" Name="alternate_id_seq" />
</Results>
<Ordering>
<Order Direction="Descending" Source="pd" Name="alternate_id_seq" />
</Ordering>
</Query>
<WhereCondition>[pd].[alternate_id] Like [prefix] & "*"</WhereCondition>
</Data>
<Statements>
<Action Name="SetLocalVar">
<Argument Name="Name">next_seq</Argument>
<Argument Name="Value">[pd].[alternate_id_seq]+1</Argument>
</Action>
</Statements>
</LookUpRecord>
<Action Name="SetField">
<Argument Name="Field">alternate_id_seq</Argument>
<Argument Name="Value">[next_seq]</Argument>
</Action>
<Action Name="SetField">
<Argument Name="Field">alternate_id</Argument>
<Argument Name="Value">[prefix] & [next_seq]</Argument>
</Action>
</Statements>
</If>
</ConditionalBlock>
</Statements>
</DataMacro>
</DataMacros>
Now when new rows are added to the table the [alternate_id_seq] and [alternate_id] columns will be populated automatically.
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