{
  "name": "16_set_nullable",
  "operations": [
    {
      "alter_column": {
        "table": "reviews",
        "column": "review",
        "nullable": false,
        "up": "(SELECT CASE WHEN review IS NULL THEN product || ' is good' ELSE review END)",
        "down": "review"
      }
    }
  ]
}