SQL Server 2019

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CREATE TABLE mytable(
   LotNumber  INTEGER  NOT NULL 
  ,ItemNumber INTEGER  NOT NULL
  ,ItemName   VARCHAR(11) NOT NULL
);
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (76,1,'WidgetRight');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (76,1,'WidgetLeft');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (76,2,'WidgetRight');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (76,2,'WidgetLeft');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (76,7,'WidgetRight');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (76,7,'WidgetLeft');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (76,9,'WidgetRight');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (76,10,'WidgetRight');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (76,10,'WidgetLeft');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (80,3,'WidgetRight');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (80,3,'WidgetLeft');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (80,7,'WidgetRight');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (80,7,'WidgetLeft');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (80,11,'WidgetRight');
INSERT INTO mytable(LotNumber,ItemNumber,ItemName) VALUES (80,31,'WidgetRight');

15 rows affected

LotNumber	ItemNumber	ItemName	newfield
76	1	WidgetRight	1
76	1	WidgetLeft	1
76	2	WidgetRight	2
76	2	WidgetLeft	2
76	7	WidgetRight	1
76	7	WidgetLeft	1
76	9	WidgetRight	2
76	10	WidgetRight	1
76	10	WidgetLeft	1
80	3	WidgetRight	2
80	3	WidgetLeft	2
80	7	WidgetRight	1
80	7	WidgetLeft	1
80	11	WidgetRight	2
80	31	WidgetRight	1