In postgresql allowed array types or integer and text.But i need to create array of objects.how can i do that.
myarray text[]; //for text ['a','b','c']
myarray integer[]; //for integer[1,2,3]
I need to create the array like below
[{'dsad':1},{'sdsad':34.6},{'sdsad':23}]
I dont want to use JSON type.Using array type i need to store the array of objects.
If you're running Postgres 9.2+, you can use the JSON type.
For example, we could do
create table jsontest (id serial primary key, data json);
insert into jsontest (data) values ('[{"dsad":1},{"sdsad":34.6},{"sdsad":23}]');
And query the data with
select data->1 from jsontest;
{"sdsad":34.6}
You say:
I dont want to use JSON type
but you cannot use an ordinary array, as PostgreSQL arrays must be of homogenous types. You can't have a 2-dimensional array of text and integer.
What you could do if you don't want to use json is to create a composite type:
CREATE TYPE my_pair AS (blah text, blah2 integer);
SELECT ARRAY[ ROW('dasd',2), ROW('sdsad', 34.6), ROW('sdsad', 23) ]::my_pair[]
which will emit:
array
----------------------------------------
{"(dasd,2)","(sdsad,35)","(sdsad,23)"}
(1 row)
If you don't want that, then json is probably your best bet. Or hstore:
SELECT hstore(ARRAY['a','b','c'], ARRAY[1,2,3]::text[])
hstore
------------------------------
"a"=>"1", "b"=>"2", "c"=>"3"
(1 row)
JSON is your preferred answer, but more info as to why.
You can do something like:
SELECT array_agg(v)
FROM mytable v;
However you get something that looks like this:
{"(dsad,1)","(sdsad,34.6)","(""sdsad,var"",23)"}
It is then up to you to know how to decode this (i.e. column order). This is possible to do programmatically but is much easier with JSON.
It's hacky, but what about using an array for each property in the object (and its corresponding scalar type). If you have a data model layer in your get/read you could put the arrays "back together" into an array of objects and in your save method you would break you objects apart into synchronized arrays. This might be complicated by your example of each object not having the same properties; IDK how you'd store undefined for a property unless you're willing for null to be the same semantically.
It's not entirely clear if you mean json:
# select '[{"dsad":1},{"sdsad":34.6},{"sdsad":23}]'::json;
json
------------------------------------------
[{"dsad":1},{"sdsad":34.6},{"sdsad":23}]
(1 row)
Or an array of json:
# select array['{"dsad":1}', '{"sdsad":34.6}', '{"sdsad":23}']::json[];
array
------------------------------------------------------
{"{\"dsad\":1}","{\"sdsad\":34.6}","{\"sdsad\":23}"}
(1 row)
Or perhaps hstore? If the latter, it's only for key-values pairs, but you can likewise use an array of hstore values.
You can do something like:
SELECT JSON_AGG(v) FROM mytable v;
However you get something that looks like this:
["00000000-0000-0000-0000-000000000001","00000000-0000-0000-0000-000000000002", "00000000-0000-0000-0000-000000000003"]
exemple :
SELECT title, (select JSON_AGG(v.video_id) FROM videos v WHERE v.channel_id = c.channel_id) AS videos FROM channel AS c
Use text[] myarray insted of myarray text[].
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
This seems like it would be straightforward to do but I just can not figure it out. I have a query that returns an ARRAY of strings in one of the columns. I want that array to only contain unique strings. Here is my query:
SELECT
f."_id",
ARRAY[public.getdomain(f."linkUrl"), public.getdomain(f."sourceUrl")] AS file_domains,
public.getuniqdomains(s."originUrls", s."testUrls") AS source_domains
FROM
files f
LEFT JOIN
sources s
ON
s."_id" = f."sourceId"
Here's an example of a row from my return table
_id
file_domains
source_domains
2574873
{cityofmontclair.org,cityofmontclair.org}
{cityofmontclair.org}
I need file_domains to only contain unique values, IE a 'set' instead of a 'list'. Like this:
_id
file_domains
source_domains
2574873
{cityofmontclair.org}
{cityofmontclair.org}
Use a CASE expression:
CASE WHEN public.getdomain(f."linkUrl") = public.getdomain(f."sourceUrl")
THEN ARRAY[public.getdomain(f."linkUrl")]
ELSE ARRAY[public.getdomain(f."linkUrl"), public.getdomain(f."sourceUrl")]
END
I have a table containing a json column. The json values will look something like this:
{'john': 1, 'alex' : 4, 'harry' :2}
If I wanted to add 1 to john, how would I go about doing this?
demo:db<>fiddle
UPDATE mytable -- 6
SET mydata = jsonb_set( -- 4
mydata::jsonb, -- 1
'{john}', -- 2
((mydata ->> 'john')::int + 1)::text::jsonb -- 3
)::json; -- 5
Fetch your data. If it is of type json, cast it into type jsonb
Path to your requested element as text array
Fetch the original value. ->> operator returns type text, so to do an integer operation, you need to cast it into type int. Then add the 1. This result must be reconverted into type jsonb. Unfortunately type int cannot be cast into type jsonb directly, so take the intermediate step via type text
Use jsonb_set() to update the JSON object specified in (1)
If your column is of type json instead of jsonb, cast the result back into type json
Perform the update
I have column options with type jsonb , in format {"names": ["name1", "name2"]} which was created with
UPDATE table1 t1 SET options = (SELECT jsonb_build_object('names', names) FROM table2 t2 WHERE t2.id= t1.id)
and where names have type jsonb array.
SELECT jsonb_typeof(names) FROM table2 give array
Now I want to extract value of names as jsonb array. But query
SELECT jsonb_build_array(options->>'names') FROM table
gave me ["[\"name1\", \"name2\"]"], while I expect ["name1", "name2"]
How can I get value in right format?
The ->> operator will return the value of the field (in your case, a JSON array) as a properly escaped text. What you are looking for is the -> operator instead.
However, note that using the jsonb_build_array on that will return an array containing your original array, which is probably not what you want either; simply using options->'names' should get you what you want.
Actually, you don't need to use jsonb_build_array() function.
Use select options -> 'names' from table; This will fix your issue.
jsonb_build_array() is for generating the array from jsonb object. You are following wrong way. That's why you are getting string like this ["[\"name1\", \"name2\"]"].
Try to execute this sample SQL script:
select j->'names'
from (
select '{"names": ["name1", "name2"]}'::JSONB as j
) as a;
I've got a column in a table that's a json. It contains only values without keys like
Now I'm trying to split the data from the json and create new table using every index of each array as new entry like
I've already tried
SELECT JSON_QUERY(abc) as 'Type', Id as 'ValueId' from Table FOR JSON AUTO
Is there any way to handle splitting given that some arrays might be empty and look like
[]
?
A fairly simply approach would be to use outer apply with openjson.
First, create and populate sample table (Please save us this step in your future questions):
DECLARE #T AS TABLE
(
Id int,
Value nvarchar(20)
)
INSERT INTO #T VALUES
(1, '[10]'),
(2, '[20, 200]'),
(3, '[]'),
(4, '')
The query:
SELECT Id, JsonValues.Value
FROM #T As t
OUTER APPLY
OPENJSON( Value ) As JsonValues
WHERE ISJSON(t.Value) = 1
Results:
Id Value
1 10
2 20
2 200
3 NULL
Note the ISJSON condition in the where clause will prevent exceptions in case the Value column contains anything other than a valid json (an empty array [] is still considered valid for this purpose).
If you don't want to return a row where the json array is empty, use cross apply instead of outer apply.
Your own code calling for FOR JSON AUTO tries to create JSON out of tabular data. But what you really needs seems to be the opposite direction: You want to transform JSON to a result set, a derived table. This is done by OPENJSON.
Your JSON seems to be a very minimalistic array.
You can try something along this.
DECLARE #json NVARCHAR(MAX) =N'[1,2,3]';
SELECT * FROM OPENJSON(#json);
The result returns the zero-based ordinal position in key, the actual value in value and a (very limited) type-enum.
Hint: If you want to use this against a table's column you must use APPLY, something along
SELECT *
FROM YourTable t
OUTER APPLY OPENJSON(t.TheJsonColumn);