QGIS/resources/function_help/json/concatenate_unique

{
  "name": "concatenate_unique",
  "type": "function",
  "groups": ["Aggregates"],
  "description": "Returns all unique strings from a field or expression joined by a delimiter.",
  "arguments": [
	{"arg":"expression", "description":"sub expression of field to aggregate"},
	{"arg":"group_by", "optional":true, "description":"optional expression to use to group aggregate calculations"},
	{"arg":"filter", "optional":true, "description":"optional expression to use to filter features used to calculate aggregate"},
	{"arg":"concatenator", "optional":true, "description":"optional string to use to join values. Empty by default."},
	{"arg":"order_by", "optional":true, "description":"optional expression to use to order features used to calculate aggregate. By default, the features will be returned in an unspecified order."}
  ],
  "examples": [
	{ "expression":"concatenate_unique(\"town_name\",group_by:=\"state\",concatenator:=',')", "returns":"comma separated list of unique town_names, grouped by state field"}
  ]
}