平凡的CASE缩写

-- With Settings.transformPatternsTrivialCaseAbbreviation active, this:
SELECT
  NVL(NULL, a),
  NVL(1, a),
  COALESCE(NULL, NULL, a),
  COALESCE(1, a, b),
  NULLIF(a, a),
  NULLIF(NULL, a),
  NULLIF(a, NULL)
FROM tab;

-- ... is transformed into the equivalent expression:
SELECT
  a,    -- NVL(NULL, a),
  1,    -- NVL(1, a),
  a,    -- COALESCE(NULL, NULL, a),
  1,    -- COALESCE(1, a, b),
  NULL, -- NULLIF(a, a),
  NULL, -- NULLIF(NULL, a),
  a     -- NULLIF(a, NULL)
FROM tab;