Is it possible to re-map integer values from a Postgres array column in the select? This is what I have:
select unnest(tag_ids) from mention m where id = 288201;
unnest
---------
-143503
-143564
125192
143604
137694
tag_ids is integer[] column
I would like to translate those numbers. Functions like abs(unnest(..)) work but found I cannot use a CASE statement. Tx.
If you want to do anything non-trivial with the elements from an array after unnesting, use the set-returning function like table:
select u.tag_id
from mention m
cross join unnest(m.tag_ids) as u(tag_id)
where m.id = 288201;
Now, u.tag_id is an integer column that you can use like any other column, e.g. in a CASE expression.
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
Say I have a varchar column let's say religions that looks like this: ["Christianity", "Buddhism", "Judaism"] (yes it has a bracket in the string) and I want the string (not array) split into multiple rows like "Christianity", "Buddhism", "Judaism" so it can be used in a WHERE clause.
Eventually I want to use the results of the query in a where clause like this:
SELECT ...
FROM religions
WHERE name in
(
<this subquery>
)
How can one do this?
You can use the function JSON_PARSE to convert the varchar string into an array. Then you can use the strategy described in Convert varchar array to rows in redshift - Stack Overflow to convert the array to separate rows.
You can do the following.
Create a temporary table with sequence of numbers
Using the sequence and split_part function available in redshift, you can split the values based on the numbers generated in the temporary table by doing a cross join.
To replace the double quote and square brackets, you can use the regexp_replace function in Redshift.
create temp table seq as
with recursive numbers(NUMBER) as
(
select 1 UNION ALL
select NUMBER + 1 from numbers where NUMBER < 28
)
select * from numbers;
select regexp_replace(split_part(val,',',seq.number),'[]["]','') as value
from
(select '["christianity","Buddhism","Judaism"]' as val) -- You can select the actual column from the table here.
cross join
seq
where seq.number <= regexp_count(val,'[,]')+1;
I have a details table with adeet column defined as jsonb[]
a sample value stored in adeet column is as below image
Sample data stored in DB :
I want to return the rows which satisfies id=26088 i.e row 1 and 3
I have tried array operations and json operations but it does'nt work as required. Any pointers
Obviously the type of the column adeet is not of type JSON/JSONB, but maybe VARCHAR and we should fix the format so as to convert into a JSONB type. I used replace() and r/ltrim() funcitons for this conversion, and preferred to derive an array in order to use jsonb_array_elements() function :
WITH t(jobid,adeet) AS
(
SELECT jobid, replace(replace(replace(adeet,'\',''),'"{','{'),'}"','}')
FROM tab
), t2 AS
(
SELECT jobid, ('['||rtrim(ltrim(adeet,'{'), '}')||']')::jsonb as adeet
FROM t
)
SELECT t.*
FROM t2 t
CROSS JOIN jsonb_array_elements(adeet) j
WHERE (j.value ->> 'id')::int = 26088
Demo
You want to combine JSONB's <# operator with the generic-array ANY construct.
select * from foobar where '{"id":26088}' <# ANY (adeet);
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'm trying to decipher another programmer's code who is long-gone, and I came across a select statement in a stored procedure that looks like this (simplified) example:
SELECT #Table2.Col1, Table2.Col2, Table2.Col3, MysteryColumn = CASE WHEN y.Col3 IS NOT NULL THEN #Table2.MysteryColumn - y.Col3 ELSE #Table2.MysteryColumn END
INTO #Table1
FROM #Table2
LEFT OUTER JOIN (
SELECT Table3.Col1, Table3.Col2, Col3 = SUM(#Table3.Col3)
FROM Table3
INNER JOIN #Table4 ON Table4.Col1 = Table3.Col1 AND Table4.Col2 = Table3.Col2
GROUP BY Table3.Col1, Table3.Col2
) AS y ON #Table2.Col1 = y.Col1 AND #Table2.Col2 = y.Col2
WHERE #Table2.Col2 < #EnteredValue
My question, what does the fourth column of the primary selection do? does it produce a boolean value checking to see if the values are equal? or does it set the #Table2.MysteryColumn equal to some value and then inserts it into #Table1? Or does it just update the #Table2.MysteryColumn and not output a value into #Table1?
This same thing seems to happen inside of the sub-query on the third column, and I am equally at a loss as to what that does as well.
MysteryColumn = gives the expression a name also called a column alias. The fact that a column in the table#2 also has the same name is besides the point.
Since it uses INTO syntax it also gives the column its name in the resulting temporary table. See the SELECT CLAUSE and note | column_alias = expression and the INTO CLAUSE