text: -- setup:
  CREATE TABLE test (a int unique, b int);
  
  -- test: same value
  INSERT INTO test (a, b) VALUES (1, 1); 
  INSERT INTO test (a, b) VALUES (1, 1);
  -- error:
  
  -- test: same value, same statement
  INSERT INTO test (a, b) VALUES (1, 1), (1, 1);
  -- error:
  
  -- test: different values
  INSERT INTO test (a, b) VALUES (1, 1), (2, 2);
  /* result:
  {a: 1, b: 1}
  {a: 2, b: 2}
  */
  
  -- test: NULL
  INSERT INTO test (b) VALUES (1), (2);
  INSERT INTO test (a, b) VALUES (NULL, 3);
  SELECT a, b FROM test;
  /* result:
  {a: NULL, b: 1}
  {a: NULL, b: 2}
  {a: NULL, b: 3}
  */
  