如何在sql中为函数选择没有行id和列名的结果值？

我做pgRouting，我需要从我的

选择

将整数结果插入dijkstra算法

SELECT ST_AsGeoJSON(ST_Transform(way, 4326)) AS geometry
  FROM pgr_dijkstra(
'SELECT osm_id AS id, source, target, st_length(way) as cost FROM planet_osm_roads',
34, 3000, false
  ) as di
  JOIN planet_osm_roads pt
  ON di.edge = pt.osm_id ;

这是可行的，但如果我想用此查询替换dijkstra函数中的节点34，例如用my street的节点号：

SELECT pl.source::integer 
FROM planet_osm_roads pl 
WHERE pl.name LIKE ''street_name'' 
LIMIT 1

加在一起：

SELECT ST_AsGeoJSON(ST_Transform(way, 4326)) AS geometry
  FROM pgr_dijkstra(
'SELECT osm_id AS id, source, target, st_length(way) as cost FROM planet_osm_roads',
'SELECT pl.source::integer FROM planet_osm_roads pl WHERE pl.name LIKE ''street_name'' LIMIT 1',
 3000, false
  ) as di
  JOIN planet_osm_roads pt
  ON di.edge = pt.osm_id ;

它将失败并出现错误：

我认为，这是因为我的select查询返回了带有行ID和列名的sql结果。但可能还有另一个问题

如何将其仅输出为单个整数

---

不要将查询作为字符串传递：

SELECT ST_AsGeoJSON(ST_Transform(way, 4326)) AS geometry
FROM pgr_dijkstra(
  'SELECT osm_id AS id, source, target, st_length(way) as cost FROM planet_osm_roads',
  (SELECT pl.source::integer FROM planet_osm_roads pl WHERE pl.name LIKE 'street_name' LIMIT 1),
   3000, false
) as di
  JOIN planet_osm_roads pt
  ON di.edge = pt.osm_id;

或者使用派生表

SELECT ST_AsGeoJSON(ST_Transform(way, 4326)) AS geometry
FROM (
  SELECT pl.source::integer as source
  FROM planet_osm_roads pl 
  WHERE pl.name 
  LIKE 'street_name' LIMIT 1
) pl 
  join lateral pgr_dijkstra(
    'SELECT osm_id AS id, source, target, st_length(way) as cost FROM planet_osm_roads',
    pl.source,
    3000, false
  ) as di on true
  JOIN planet_osm_roads pt ON di.edge = pt.osm_id;

---

不要将查询作为字符串传递：

SELECT ST_AsGeoJSON(ST_Transform(way, 4326)) AS geometry
FROM pgr_dijkstra(
  'SELECT osm_id AS id, source, target, st_length(way) as cost FROM planet_osm_roads',
  (SELECT pl.source::integer FROM planet_osm_roads pl WHERE pl.name LIKE 'street_name' LIMIT 1),
   3000, false
) as di
  JOIN planet_osm_roads pt
  ON di.edge = pt.osm_id;

或者使用派生表

SELECT ST_AsGeoJSON(ST_Transform(way, 4326)) AS geometry
FROM (
  SELECT pl.source::integer as source
  FROM planet_osm_roads pl 
  WHERE pl.name 
  LIKE 'street_name' LIMIT 1
) pl 
  join lateral pgr_dijkstra(
    'SELECT osm_id AS id, source, target, st_length(way) as cost FROM planet_osm_roads',
    pl.source,
    3000, false
  ) as di on true
  JOIN planet_osm_roads pt ON di.edge = pt.osm_id;

---

Vertex是整数参数，您试图将文本放在那个里。 只需将“”改为（）

---

这是一种方法，另一种方法是使用street name作为参数和in参数编写函数，并将geojson作为输出。

Vertex是整数参数，您试图将文本放在那里。 只需将“”改为（）

这是一种方法，另一种方法是使用street name作为参数编写函数，并将geojson作为输出