字符串 PostgreSQL 中的变量

Question

我在 postgreSQL 数据库中编写了代码：

SELECT ST_Distance(gg1, gg2) As spheroid_dist, ST_Distance(gg1, gg2, false) As sphere_dist
FROM (SELECT
   'SRID=4326;POINT(-72.1235 42.3521)'::geography as gg1,
   'SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)'::geography as gg2
   ) As foo  ;

而不是 'POINT(-72.1235 42.3521)' 和 LINESTRING(-72.1260 42.45, -72.123 42.1546)' 我想添加一个从表中选择的点：

SELECT ST_asText(geog) FROM punkty WHERE gid = 1

如何将选定的变量添加到 psql 数据库中的字符串中？

Answer 1

欢迎来到 SO。

我可能会过度简化您的问题，但只需在 where 子句或连接（如果可能）中添加两个表就可以了。

例子：

SELECT 
  ST_Distance(t1.geog, t2.geog) As spheroid_dist, 
  ST_Distance(t1,geog, t2.geog, false) As sphere_dist
FROM 
  punkty2 t1, punkty2 t2 
WHERE t1.gid = 1 AND t2.gid = 2