Question

我有一个（相当冗长的）select query我需要在未知名称的表上运行才能返回另一个表。有没有办法使用dynamic commands执行此操作？

我在%I上一直收到语法错误：

功能：

CREATE OR REPLACE FUNCTION angles(table_name TEXT)
  RETURNS TABLE (id int, name varchar, polygon_num int, point_order int) AS 
$BODY$
BEGIN
  RETURN QUERY EXECUTE 'select id,
       name,
       polygon_num,
       point_order as vertex,
       --
       case when point_order = 1
         then last_value(ST_Astext(ST_Makeline(sp,ep))) over (partition by id, polygon_num)
         else lag(ST_Astext(ST_Makeline(sp,ep)),1) over (partition by id, polygon_num order by point_order)
       end ||' - '||ST_Astext(ST_Makeline(sp,ep)) as lines,
       --
       abs(abs(
       case when point_order = 1
         then last_value(degrees(ST_Azimuth(sp,ep))) over (partition by id, polygon_num)
         else lag(degrees(ST_Azimuth(sp,ep)),1) over (partition by id, polygon_num order by point_order)
       end - degrees(ST_Azimuth(sp,ep))) -180 ) as ang
from (-- 2.- extract the endpoints for every 2-point line segment for each linestring
      --     Group polygons from multipolygon
      select id,
             name,
             coalesce(path[1],0) as polygon_num,
             generate_series(1, ST_Npoints(geom)-1) as point_order,
             ST_Pointn(geom, generate_series(1, ST_Npoints(geom)-1)) as sp,
             ST_Pointn(geom, generate_series(2, ST_Npoints(geom)  )) as ep
      from ( -- 1.- Extract the individual linestrings and the Polygon number for later identification
             select id,
                    name,
                    (ST_Dump(ST_Boundary(the_geom))).geom as geom,
                    (ST_Dump(ST_Boundary(the_geom))).path as path -- To identify the polygon
              from %I ) as pointlist ) as segments';


END;
$BODY$
LANGUAGE plpgsql;

查询：

SELECT angles('poly_and_multipoly');

Answer 1

您忽略了format函数来格式化字符串。

％我是format函数的参数，在这里你只是试图执行碰巧有％I的文字字符串。

EXECUTE format('UPDATE tbl SET %I = $1 WHERE key = $2', colname)
    USING newvalue, keyvalue;

在这里，您可以看到colname是format函数的参数，而newvalue和keyvalue是结果SQL查询的参数。

因此，使用正确的参数将您的字符串包装在format函数中，您应该很高兴。

表名作为PostgreSQL参数 - 使用％I的语法错误

1 个答案: