MySQL 8.0

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CREATE TABLE tablename (`SN` VARCHAR(14), `tx_id` INTEGER, `pa3` VARCHAR(14), `pa4` VARCHAR(15));

INSERT INTO tablename (`SN`, `tx_id`, `pa3`, `pa4`) VALUES
  ('I2120210007014', '149362', 'V16F2021117016', 'V15S2021145018'),
  ('I2120210007014', '149362', 'V15S2021144019', 'V15S2021145018'),
  ('I2120210007014', '149362', 'V16F2021117017', 'V15S2021145018'),
  ('I2120210007014', '149362', 'V16F2021117017', 'V15S2021145018'),
  ('I2120210007014', '149362', 'V16F2021117017', 'V15S2021145018'),
  ('I2120210007014', '148716', 'V15C2021116010', 'V15C20211091016');
SELECT SN, tx_id,
       COUNT(DISTINCT CASE WHEN pa LIKE 'V16F%' THEN pa END) V16F,
       COUNT(DISTINCT CASE WHEN pa LIKE 'V15S%' THEN pa END) V15S,
       COUNT(DISTINCT CASE WHEN pa LIKE 'V15C%' THEN pa END) V15C
FROM (
  SELECT SN, tx_id, pa3 pa FROM tablename
  UNION ALL
  SELECT SN, tx_id, pa4 pa FROM tablename
) t  
GROUP BY SN, tx_id


SN
tx_id
V16F
V15S
V15C


I2120210007014
148716
0
0
2

I2120210007014
149362
2
2
0


SELECT SN, tx_id,
       COUNT(CASE WHEN pa LIKE 'V16F%' THEN pa END) V16F,
       COUNT(CASE WHEN pa LIKE 'V15S%' THEN pa END) V15S,
       COUNT(CASE WHEN pa LIKE 'V15C%' THEN pa END) V15C
FROM (
  SELECT SN, tx_id, pa3 pa FROM tablename
  UNION 
  SELECT SN, tx_id, pa4 pa FROM tablename
) t  
GROUP BY SN, tx_id


SN
tx_id
V16F
V15S
V15C


I2120210007014
149362
2
2
0

I2120210007014
148716
0
0
2


SELECT SN, tx_id,
       SUM(pa LIKE 'V16F%') V16F,
       SUM(pa LIKE 'V15S%') V15S,
       SUM(pa LIKE 'V15C%') V15C
FROM (
  SELECT SN, tx_id, pa3 pa FROM tablename
  UNION 
  SELECT SN, tx_id, pa4 pa FROM tablename
) t  
GROUP BY SN, tx_id


SN
tx_id
V16F
V15S
V15C


I2120210007014
149362
2
2
0

I2120210007014
148716
0
0
2


SELECT SN, tx_id,
       COUNT(DISTINCT CASE WHEN pa3 LIKE 'V16F%' THEN pa3 END) +
       COUNT(DISTINCT CASE WHEN pa4 LIKE 'V16F%' THEN pa4 END) -
       SUM(pa3 = pa4) V16F,
       COUNT(DISTINCT CASE WHEN pa3 LIKE 'V15S%' THEN pa3 END) +
       COUNT(DISTINCT CASE WHEN pa4 LIKE 'V15S%' THEN pa4 END) -
       SUM(pa3 = pa4) V15S,
       COUNT(DISTINCT CASE WHEN pa3 LIKE 'V15C%' THEN pa3 END) +
       COUNT(DISTINCT CASE WHEN pa4 LIKE 'V15C%' THEN pa4 END) -
       SUM(pa3 = pa4) V15C
FROM tablename
GROUP BY SN, tx_id


SN
tx_id
V16F
V15S
V15C


I2120210007014
148716
0
0
2

I2120210007014
149362
2
2
0