Approving "One" in a one-to-many DB relationship only when ALL "Many"s are approved - sql

Question

I've tried looking for this I promise, but its kind of a hard question to search for...
I have a database with two tables linked in a one-to-many relationship where each "one" is an invoice header linked to "many" invoice lines.
I am designing a tool that will match each invoice line to a purchase order and I want to be able to mark an invoice header as "matched" only when all lines have been matched.
Does anyone know how to write this update query?

Answer 1

The relational operator you seek is known formally as division and colloquially as "the suppliers who supply all parts". For various reasons, a division operator has not appeared in any SQL product I know of, Access included. Instead, you need to use other operators in combination to do the same. See Divided we stand: the SQL of relational division by Joe Celko.

Answer 2

An approach available to users of Access 2010 and later is to use event-driven data macros in the child table to maintain the status flag in the parent table. For example, with a parent table
[InvHeader]
InvID AllMatched
----- ----------
1 No
and a child table
[InvItem]
ItemID InvID Matched
------ ----- -------
1 1 Yes
2 1 No
the following After Update data macro will automatically update the corresponding row in [InvHeader] after a child row has been changed in [InvItem]
Code:
<?xml version="1.0" encoding="UTF-16" standalone="no"?>
<DataMacros xmlns="http://schemas.microsoft.com/office/accessservices/2009/11/application">
<DataMacro Event="AfterUpdate">
<Statements>
<Action Collapsed="true" Name="SetLocalVar">
<Argument Name="Name">newAllMatched</Argument>
<Argument Name="Value">True</Argument>
</Action>
<ForEachRecord>
<Data Alias="i">
<Reference>InvItem</Reference>
<WhereCondition>[i].[InvID]=[InvItem].[InvID]</WhereCondition>
</Data>
<Statements>
<ConditionalBlock>
<If>
<Condition>Not [i].[Matched]</Condition>
<Statements>
<Action Collapsed="true" Name="SetLocalVar">
<Argument Name="Name">newAllMatched</Argument>
<Argument Name="Value">False</Argument>
</Action>
<Action Name="ExitForEachRecord"/>
</Statements>
</If>
</ConditionalBlock>
</Statements>
</ForEachRecord>
<LookUpRecord>
<Data Alias="hdr">
<Reference>InvHeader</Reference>
<WhereCondition>[hdr].[InvID]=[InvItem].[InvID]</WhereCondition>
</Data>
<Statements>
<ConditionalBlock>
<If>
<Condition>[hdr].[AllMatched]<>[newAllMatched]</Condition>
<Statements>
<EditRecord>
<Data Alias="hdr"/>
<Statements>
<Action Collapsed="true" Name="SetField">
<Argument Name="Field">AllMatched</Argument>
<Argument Name="Value">[newAllMatched]</Argument>
</Action>
</Statements>
</EditRecord>
</Statements>
</If>
</ConditionalBlock>
</Statements>
</LookUpRecord>
</Statements>
</DataMacro>
</DataMacros>
Note that this is an example for updates only. For completeness, one would normally put the above code in a named data macro and call it from After Insert, After Update, and After Delete.