SQLite 3.27

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CREATE TABLE myTable (`Col1` VARCHAR(4), `Col2` VARCHAR(4), `Col3` INT);
✓
INSERT INTO myTable (`Col1`, `Col2`, `Col3`) VALUES
  ('R1', 'C1', 5),
  ('R2', 'C3', 8),
  ('R1', 'C1', 2),
  ('R1', 'C2', 4),
  ('R2', 'C5', 3),
  ('R2', 'C2', 4);
✓
SELECT Col1, Col2, COUNT(*) AS cnt, SUM(Col3) AS total FROM myTable GROUP BY Col1, Col2
UNION ALL 
SELECT Col1, NULL, COUNT(*), SUM(Col3) FROM myTable GROUP BY Col1 
ORDER BY Col1


Col1
Col2
cnt
total


R1
C1
2
7

R1
C2
1
4

R1
null
3
11

R2
C2
1
4

R2
C3
1
8

R2
C5
1
3

R2
null
3
15