I want to get just radius value from ST_MinimumBoungingRadius.
Something like this (from postgresql documentation) works just fine:
SELECT radius
FROM
ST_MinimumBoundingRadius('MULTIPOINT(1 2,3 8,5 6)')
So I don't understand, why doesn't work similar query on existing table:
SELECT radius
FROM
(SELECT
ST_MinimumBoundingRadius(ST_Collect(geom)) minrad
FROM a) b
Result of this query is ERROR: column "radius" does not exist
Is there any way to extract just radius value?
The main difference is that in the first case you are calling the function in the FROM clause while in the second it is in the select clause. In the first case, the result is made of two column while in the later it is a string aggregation of all columns.
You can fix it by using the function in the FROM clause again, using either a double-parenthesis or a lateral join:
SELECT radius
FROM ST_MinimumBoundingRadius((SELECT ST_Collect(geom)
FROM a)) minrad;
or
SELECT radius
FROM (SELECT ST_Collect(geom) geom FROM a) tbla,
LATERAL ST_MinimumBoundingRadius(tbla.geom) minrad;
Related
how are you?
I needed to store an array of numbers as JSONB in PostgreSQL.
Now I'm trying to calculate stats moments from this JSON, I'm facing some issues.
Sample of my data:
I already was able to convert a JSON into a float array.
I used a function to convert jsonb to float array.
CREATE OR REPLACE FUNCTION jsonb_array_castdouble(jsonb) RETURNS float[] AS $f$
SELECT array_agg(x)::float[] || ARRAY[]::float[] FROM jsonb_array_elements_text($1) t(x);
$f$ LANGUAGE sql IMMUTABLE;
Using this SQL:
with data as (
select
s.id as id,
jsonb_array_castdouble(s.snx_normalized) as serie
FROM
spectra s
)
select * from data;
I found a function that can do these calculations and I need to pass an array for that: https://github.com/ellisonch/PostgreSQL-Stats-Aggregate/
But this function requires an array in another way: unnested
I already tried to use unnest, but it will get only one value, not the entire array :(.
My goal is:
Be able to apply stats moment (kurtosis, skewness) for each row.
like:
index
skewness
1
21.2131
2
1.123
Bonus: There is a way to not use this 'with data', use the transformation in the select statement?
snx_wavelengths is JSON, right? And also you provided it as a picture and not text :( the data looks like (id, snx_wavelengths) - I believe you meant id saying index (not a good idea to use a keyword, would require identifier doublequotes):
1,[1,2,3,4]
2,[373,232,435,84]
If that is right:
select id, (stats_agg(v::float)).skewness
from myMeasures,
lateral json_array_elements_text(snx_wavelengths) v
group by id;
DBFiddle demo
BTW, you don't need "with data" in the original sample if you don't want to use and could replace with a subquery. ie:
select (stats_agg(n)).* from (select unnest(array[16,22,33,24,15])) data(n)
union all
select (stats_agg(n)).* from (select unnest(array[416,622,833,224,215])) data(n);
EDIT: And if you needed other stats too:
select id, "count","min","max","mean","variance","skewness","kurtosis"
from myMeasures,
lateral (select (stats_agg(v::float)).* from json_array_elements_text(snx_wavelengths) v) foo
group by id,"count","min","max","mean","variance","skewness","kurtosis";
DBFiddle demo
I have two instances of the type integer[] (generated by the Timescale histogram function), e.g. {3,5,1} and {2,2,2}.
I would like to add these two Arrays to {5,7,3} but using
SELECT "ID", histogram(...) + histogram(...)
FROM "ID"
GROUP BY "ID"
throws the following error: operator does not exist: integer[] + integer[]. Is there any way to accomplish this?
I don't think there is such a function.
In order to achieve your goal (in SQL) you'd have to unnest the arrays, then add the corresponding elements and aggregate the results back to array.
SELECT
array_agg(
COALESCE(h1.val, 0)+COALESCE(h2.val, 0)
ORDER BY COALESCE(h1.row_number, h2.row_number)
) as result
FROM
(SELECT ROW_NUMBER() over (), val FROM unnest('{3,5,1,5}'::int[]) as val) as h1
FULL JOIN (SELECT ROW_NUMBER() over (), val FROM unnest('{2,2,2}'::int[]) as val) as h2 ON h1.row_number=h2.row_number
I'm using ROW_NUMBER window function to get the array element number.
FULL JOIN is required because the arrays may be of different length. It is also the reason why COALESCE is required when adding the elements.
Thanks to #a_horse_with_no_name the query may be rewritten using ordinality without relying on row_number() function:
SELECT
array_agg(
COALESCE(h1.val, 0)+COALESCE(h2.val, 0)
ORDER BY COALESCE(h1.no, h2.no)
) as result
FROM
unnest('{3,5,1,5}'::int[]) WITH ORDINALITY as h1(val, no)
FULL JOIN unnest('{2,2,2}'::int[]) WITH ORDINALITY as h2(val, no) ON h1.no=h2.no
does anyone know how to introduce wildcards (e.g. %% ) when querying a jsonb column that in this case is an array at the top level ? would also like to ignore casee
select * from "food" where (type #> '"xyz"')
You need to unnest the array:
select f.*
from food f
where exists (select *
from jsonb_array_elements_text(f.type) as x(typ)
where x.typ like '%xyz%');
One option would be applying a CROSS JOIN between the table and unnested array elements without a subquery as
SELECT j.*
FROM food f
CROSS JOIN jsonb_array_elements(type) AS j
WHERE value::text like '%"xyz"%'
Demo
thanks folks.. this seems to do the trick:
SELECT *
FROM
food,
jsonb_array_elements(type) as types
WHERE types::text ilike '%xyz%';```
I am trying to transform all the roundabouts in a city into simple intersections/crossroads (o -> +). As I am using OpenStreetMap for the initial topology, some roundabouts are not a circle but just the segments of the circle (Ex: https://www.openstreetmap.org/#map=18/43.34516/-8.41536).
In practice the problem is that I need the centroid of each roundabout and I get it almost in all cases but sometimes I get several centroids for the same roundabout (centroids of the arches, no the full roundabout).
I have achieved this:
select f.osm_id as fid, (select ST_CENTROID(ST_Buffer(ST_UNION(way),1)) as r_geom
from planet_osm_line d
where st_intersects(f.way, d.way) and junction = 'roundabout') as rotonda
from planet_osm_line f
where junction like 'roundabout';
But this does not resolve the problem, it only reduces it. I am not getting the full circle, just bigger segments of it.
So I guess I need a recursive query in order to do this until the number of geometries retrieved remains the same (the full circle). Any ideas about how to build this query?
I was looking for something like this (hope it helps others in need):
create table no_roundabouts as
with recursive roundabout(geom) as (--Recursive function to build closed circled roundabouts even with roundabouts mapped as differents arches.
SELECT ST_TRANSFORM(way,3857)
FROM planet_osm_line ways --Get all segments tagged as 'roundabout'
WHERE ways.junction = 'roundabout'
UNION ALL
SELECT ST_TRANSFORM(ST_UNION(ways.way, roundabout.geom),3857)
FROM roundabout, planet_osm_line ways -- Compose segments building greater arches of the roundabout until we have the full circle (My_segment + a touching segment that is no contained in my segment)
WHERE ways.junction = 'roundabout' and ST_INTERSECTS(roundabout.geom, ways.way) and not ST_CONTAINS(roundabout.geom, ways.way)
)
SELECT * FROM roundabout;
alter table no_roundabouts add column id bigserial; -- Add id to each line
delete from no_roundabouts a -- Delete repeated roundabouts generated during recursion
where exists (select geom from no_roundabouts b where ST_CONTAINS(b.geom, a.geom) and b.id > a.id);
--select count(*) from no_roundabouts WHERE ST_IsClosed(geom) = false;
update no_roundabouts set geom = ST_LINEMERGE(geom) where ST_ISCLOSED(geom) is false --Force closed roundabouts
-- Query replacing roundabouts with crossroads (linking each way in and out with the centroid of the roundabout)
SELECT ST_TRANSFORM(ST_ADDPOINT(y.way, ST_CENTROID(x.geom), 0),4326)
FROM no_roundabouts x JOIN planet_osm_line y ON ST_INTERSECTS(y.way, x.geom)
WHERE y.highway is not null and ST_INTERSECTS(x.geom, st_pointn(y.way,1)) and ST_CONTAINS(x.geom, y.way) = false
UNION
SELECT ST_TRANSFORM(ST_ADDPOINT(y.way, ST_CENTROID(x.geom), -1),4326)
FROM no_roundabouts x JOIN planet_osm_line y ON ST_INTERSECTS(y.way, x.geom)
WHERE y.highway is not null and ST_INTERSECTS(x.geom, ST_POINTN(y.way,-1)) and ST_CONTAINS(x.geom, y.way) = false;
I have two columns in the same table that I want to join in Postgresql but for some reason I’m getting this error. Don’t know how to figure it out. Please help.
[42P01] ERROR: relation "a" does not exist
Position: 10
X table contains two pools(ABC,XYZ), ids, numbers and description. If an ID exists in one pool but not in the other, it should update description column to “ADD”. Pools need to be joined on number.
UPDATE A
SET A.Description = 'ADD'
FROM X AS A
LEFT JOIN X AS B ON B.number = A.number
AND B.id = 'ABC'
WHERE A.id = 'XYZ'
AND B.number IS NULL
AND A.Description IS NULL;
With standard SQL you can't do a join as part of an update, but what you can do is include a subquery to select the id's to update. The subquery can contain a join. I'm not entirely clear on what you're actually trying to accomplish, but you could do something like this:
UPDATE x SET description='ADD' WHERE number IN (
SELECT a.number FROM x AS a
LEFT OUTER JOIN x AS b ON a.number=b.number AND a.id='XYZ' AND b.id='ABC'
WHERE b.number IS NULL
);
This will join the table x with itself and will select (and update) any numbers's that don't have a matching number in the 'ABC' and 'XYZ' zone.
PostgreSQL does have a UPDATE FROM syntax that does let you update with complex subqueries. It's more flexible but it's non-standard. You can find an example of this type of query here.