Not as eloquent as Jarmo's, but it shows a different approach
Names Default To Here( 1 );
dt = New Table( "Example",
	Add Rows( 7 ),
	Compress File When Saved( 1 ),
	New Column( "SN",
		Character,
		"Nominal",
		Set Values( {"1", "2", "3", "3", "5", "6", "6"} )
	),
	New Column( "Material Lot",
		Character,
		"Nominal",
		Set Values( {"A1", "A2", "A3", "A4", "A5", "A6", "A7"} )
	)
);
dtCombine = dt << Summary(
	Group( :SN ),
	Freq( "None" ),
	Weight( "None" ),
	Link to original data table( 0 )
);
dtCombine << New Column( "Material Lot",
	Character,
	set each value(
		Eval(
			Eval Expr(
				Concat Items(
					dt:Material Lot[dt <<
					get rows where( dt:SN == Expr( dtCombine:SN[Row()] ) )],
					", "
				)
			)
		);
	)
);

 
					
				
			
			
				
	Jim