如何使用连接返回结果？

Question

现在我有以下功能：

CREATE OR REPLACE FUNCTION set_city(_city_id bigint, _country_id integer, _lat float, lon float) RETURNS geo_cities LANGUAGE plpgsql as $$ 
    DECLARE 
      city_coords Geometry := ST_SetSrid(ST_MakePoint(_lon, _lat), 3395); 
      result record; 
    BEGIN 
      IF EXISTS (SELECT 1 FROM geo_cities gc WHERE gc.id = _city_id) 
      THEN 
        UPDATE geo_cities 
        SET coords = city_coords, country_id = _country_id 
        WHERE id = _city_id 
        RETURNING * INTO result; 
      ELSE 
        INSERT INTO geo_cities(id, country_id, coords) 
        VALUES (_city_id, _country_id, city_coords) 
        RETURNING * INTO result; 
      END IF; 
      RETURN result; 
    END; 
$$ 

我想用我的结果加入。这就是我的意思：

... 
    RETURNING 
    id as city_id, 
    ST_X(coords) as lon, 
    INNER JOIN geo_countries as gc ON gc.id = id 
    ... 

我可以那样做吗？

Answer 1

您可以加入一个函数调用表的结果，但在一个稍微不同的方式：

SELECT 
    gc.col_1, gc.col_2, /* ... as many as needed */ 
    city.id AS city_id, ST_X(city.coords) AS lon 
FROM 
    set_city(1234, 5678, 1.23, 3.45) AS city 
    JOIN geo_countries AS gc ON gc.id = city.id 

因此，在实践中，set_city(...)的行为在SELECT仅仅是如果它是任何其他种类的表。