如何通过使用几个查询从许多表中计算事物？

小编典典

如何通过使用几个查询从许多表中计算事物？

sql

注意：这个问题与PostGIS和Postgresql有关，并且是通过PHP实现的

现在我有了表A：

gid | kstart  | kend    | ctrl_sec_no | the_geom | 
626 | 238     | 239     | 120802      | 123456   |
638 | 249     | 250     | 120802      | 234567   |
4037| 239     | 249     | 120802      | 345678   |

注意：the_geom是一个几何值（类型：LINE），在这种情况下，我将它们随机化以提高可读性

和表B：

gid | ctrl_sec_no | x   | the_geom
543 | 120802      | 239 | null
544 | 120802      | 247 | null

[PostGIS描述]这两个表由ctrl_sec_no关联，这意味着来自表A的ctrl_sec_no
120802上的3条连续线，连接到一条线中，并包含来自表B的两个POINT。我们仅知道距离{MAX（kend）-MIN（线路的公里数（kstart）}和它在线路上的公里数（x）。

问题是PostgreSQL的查询是什么。

（a。）从A.kend中选择最高值，从A.kstart中选择最低值-> 250-238 = 12

（b。）从A.kend中选择最大值，然后减去B中的“ x”值-> 250-239 = 11

（c。）从这两个值（（b。）/（a。））-> 11/12计算比率

（d。）使用PostGIS：ST_Interpolate->
ST_Interpolate（A.the_geom，11/12）注意：此函数用于与LINE一起找到POINT，另一方面定义POINT所在的位置

（e。）我们将从（d。）获取一个值，并将其用于UPDATE’the_geom’列上的表B，该表最初为NULL。

（f。）对表B中的每一行循环查询。

[PostGIS描述]这组查询的目的是通过计算一些数学运算来确定表B中的the_geom并将输出放入ST_Interpolate函数中，以获取表B中POINT所在位置的the_geom。

感谢Advanced，我知道这是一个安静而复杂的问题。我不介意您是否会使用太多查询。只是为了获得正确的值。

这些是在danihp的帮助下的实际查询（最终）。

with CTE( max_kend) as (
 SELECT MAX(A.kend)
 FROM centerline A
),
r_b as (
 select B.ctrl_sec_no,B.gid, MAX(CTE.max_kend) - B.km as b
  FROM land_inventory B cross join CTE group by B.gid,B.ctrl_sec_no,B.km
),
r_a as (
    SELECT MAX(A.kend) - MIN(A.kstart) as a
    FROM centerline A
),
r_ratio as (
  select r_b.gid, r_b.b / r_a.a  as my_ratio
  from r_a cross join r_b
),
r_new_int as (
select B.gid,r_ratio.my_ratio,B.ctrl_sec_no,B.km,ST_AsText(ST_Envelope(ST_Collect(ST_line_interpolate_point(A.the_geom,  r_ratio.my_ratio )))) as new_int from centerline A, land_inventory B inner join r_ratio on B.gid = r_ratio.gid where A.ctrl_sec_no = B.ctrl_sec_no group by B.ctrl_sec_no,B.gid,r_ratio.my_ratio,B.km order by B.ctrl_sec_no
) 
UPDATE land_inventory
set land_inventory.the_geom = n.new_int
from r_new_int n
where 
  n.gid = land_inventory.gid and
  land_inventory.the_geom is NULL;

阅读 177

2021-05-16

共1个答案

小编典典

好了，走吧。

（一种）

SELECT MAX(A.kend) - MIN( A.kstart) as a
FROM Table A

（b）

编辑假设表B的gid为PK …

with CTE( max_kend, min_x) as (
 SELECT MAX(A.kend), NULL
 FROM TableA A
)
select B.gid, MAX(CTE.max_kend) - B.min_x as b
 FROM TableB B 
 cross join CTE

（C）

with CTE( max_kend, min_x) as (
 SELECT MAX(A.kend), NULL
 FROM TableA A
),
r_b as (
 select B.gid, MAX(CTE.max_kend) - B.min_x as b
  FROM TableB B 
  cross join CTE
),
r_a as (
    SELECT MAX(A.kend) - MIN( A.kstart) as a
    FROM Table A
)
select r_b.gid, r_a.a / r_b.b as my_ratio
from r_a cross join r_b

（d）

with CTE( max_kend, min_x) as (
 SELECT MAX(A.kend), NULL
 FROM TableA A
),
r_b as (
 select B.gid, MAX(CTE.max_kend) - B.min_x as b
  FROM TableB B 
  cross join CTE
),
r_a as (
    SELECT MAX(A.kend) - MIN( A.kstart) as a
    FROM Table A
),
r_ratio as (
  select r_b.gid, r_a.a / r_b.b as my_ratio
  from r_a cross join r_b
)
select ST_Interpolate(A.the_geom,  r_ratio.my_ratio )   
from TableB B 
inner join r_ratio on B.gid = r_ratio.gid

（e，f）

with CTE( max_kend, min_x) as (
 SELECT MAX(A.kend), NULL
 FROM TableA A
),
r_b as (
 select B.gid, MAX(CTE.max_kend) - B.min_x as b
  FROM TableB B 
  cross join CTE
),
r_a as (
    SELECT MAX(A.kend) - MIN( A.kstart) as a
    FROM Table A
),
r_ratio as (
  select r_b.gid, r_a.a / r_b.b as my_ratio
  from r_a cross join r_b
),
r_new_int as (
  select ST_Interpolate(A.the_geom,  r_ratio.my_ratio ) as new_int
  from TableB B 
  inner join r_ratio on B.gid = r_ratio.gid
)
UPDATE tableB
set tableB.the_geom = n.new_int
from r_new_int n
where 
  n.gid = tableB.gid and
  tableB.the_geom  is NULL

免责声明，不是睾丸。

已编辑

with CTE( max_kend) as (
 SELECT MAX(A.kend)
 FROM centerline A
),
r_b as (
 select B.ctrl_sec_no,B.gid, MAX(CTE.max_kend) - B.km as b
  FROM land_inventory B cross join CTE group by B.gid,B.ctrl_sec_no,B.km
),
r_a as (
    SELECT MAX(A.kend) - MIN(A.kstart) as a
    FROM centerline A
),
r_ratio as (
  select r_b.gid, r_b.b / r_a.a  as my_ratio
  from r_a cross join r_b
),
r_new_int as (
  select     
    B.gid,
    r_ratio.my_ratio,
    B.ctrl_sec_no,B.km,
    ST_AsText(ST_Envelope(ST_Collect(
          ST_line_interpolate_point(A.the_geom,  r_ratio.my_ratio 
    )))) as new_int 
  from 
    centerline A inner join
    land_inventory B 
       on A.ctrl_sec_no = B.ctrl_sec_no 
       inner join 
    r_ratio on B.gid = r_ratio.gid 
  group by B.ctrl_sec_no,B.gid,r_ratio.my_ratio,B.km order by B.ctrl_sec_no
) 
UPDATE land_inventory
set the_geom = n.new_int
from r_new_int n
where 
  n.gid = land_inventory.gid and
  land_inventory.the_geom is NULL;

2021-05-16