SQLite 3.27

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CREATE TABLE tablename (
  Col1 TEXT,
  Col2 TEXT,
  Col3 TEXT,
  Col4 TEXT
);
INSERT INTO tablename
  (Col1, Col2, Col3, Col4)
VALUES
  ('A', 'B', NULL, NULL),
  (NULL, 'B', 'C', NULL),
  ('A', 'B', 'C', NULL);
SELECT COUNT(DISTINCT Col1) <= 1 ok1,
       COUNT(DISTINCT Col2) <= 1 ok2,
       COUNT(DISTINCT Col3) <= 1 ok3,
       COUNT(DISTINCT Col4) <= 1 ok4
FROM tablename;       


ok1
ok2
ok3
ok4


1
1
1
1


SELECT MAX(
         COUNT(DISTINCT Col1),
         COUNT(DISTINCT Col2),
         COUNT(DISTINCT Col3),
         COUNT(DISTINCT Col4)
       ) <= 1 ok  
FROM tablename;


ok


1