QGIS/resources/function_help/json/nullif

{
  "name": "nullif",
  "type": "function",
  "description": "Returns a null value if value1 equals value2; otherwise it returns value1. This can be used to conditionally substitute values with NULL.",
  "arguments": [ {"arg":"value1", "description": "The value that should either be used or substituted with NULL."},
                 {"arg":"value2", "description": "The control value that will trigger the NULL substitution."}],
  "examples": [ { "expression":"nullif('(none)', '(none)')", "returns":"NULL"},
                { "expression":"nullif('text', '(none)')", "returns":"'text'"},
                { "expression":"nullif(\"name\", '')", "returns":"NULL, if name is an empty string (or already NULL), the name in any other case."} ]
}