PartiQL/SQL: JSON-SUPER array query to extract values to table on Redshift - sql

Question

I have a somewhat complicated SUPER array that I brought in to Redshift using a REST API. The 'API_table' currently looks like this:table example
One of the sample columns "values" reads as follows:
values
[{"value":[{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T17:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T17:45:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:15:00.000-05:00"},,{"value":"6.8","qualifiers":["P"],"dateTime":"2023-01-30T20:00:00.000-05:00"},...
I've queried the "value" data using:
SELECT c.values[0].value[0].value as v
FROM API_table c;
However, this only returns the first value "6.9" in each row and not all the "value" items in the row. The same approach doesn't work for extracting the "dateTime" items as it produced NULL values:
SELECT c.values[0].value[0].dateTime as dt
FROM API_table c;
The above example only resembles one row of the table. My question is-- are there ways to query the data in every row of the table so that all the values ("value" & "dateTime") of every row can be extracted onto a new table?
The desired result is:
v
dt
6.9
2023-01-30T17:45:00.000-05:00
6.9
2023-01-30T18:00:00.000-05:00
6.9
2023-01-30T18:15:00.000-05:00
Many thanks.
I tried the following query but it only returned singular "value' results for each row.
SELECT c.values[0].value[0].value as v
FROM API_table c;
When applied to the "dateTime" items, it yielded NULL values:
SELECT c.values[0].value[0].dateTime as dt
FROM API_table c;
===================================================================
#BillWeiner thanks, I worked through both the CTE and test case examples and got the desired results (especially with CTE). The only issue that remains is knowing how to select the original table/column that contains the entire super array so that it can be inserted into test1 (or col1 in the CTE case).
There are super arrays in every row of column 'values' so the issue remains in selecting the column 'values' and extracting each of the multiple value ("6.9") and dateTime objects from each row.
================================================================
I've managed to get the query going when the json strings are explicitly stated in the insert into test1 values query.
Now I'm running this query:
SET enable_case_sensitive_identifier TO true;
create table test1 (jvalues varchar(2048));
insert into test1 select c.values from ph_api c;
create table test2 as select json_parse(jvalues) as svalues from test1;
with recursive numbers(n) as
( select 0 as n
union all
select n + 1
from numbers n
where n.n < 20
),
exp_top as
( select c.svalues[n].value
from test2 c
cross join numbers n
)
,
exp_bot as
( select c.value[n]
from exp_top c
cross join numbers n
where c.value is not null
)
select *, value.value as v, value."dateTime" as dt
from exp_bot
where value is not null;
However, I'm getting an error--ERROR: column "jvalues" is of type character varying but expression is of type super Hint: You will need to rewrite or cast the expression. when I try to insert the source table with insert into test1 SELECT c.values from table c;
I would like to be able to SELECT this source data:
sourceinfo
variable
values
{"siteName":"YAN","siteCode":[{"value":"01"}]
{“variableCode":[{"value":"00600","network":"ID"}
[{“value":[{"value":"3.9","qualifiers":["P"],"dateTime":"2023-01-30T17:30:00.000-05:00"},{"value":"4.9","qualifiers":["P"],"dateTime":"2023-01-30T17:45:00.000-05:00"}]
{"siteName":"YAN","siteCode":[{"value":"01"}]
{“variableCode":[{"value":"00600","network":"ID"}
[{“value":[{"value":"5.9","qualifiers":["P"],"dateTime":"2023-01-30T18:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:15:00.000-05:00"}]
as the jvalues so that it could be unrolled into a desired result of:
v
dt
3.9
2023-01-30T17:30:00.000-05:00
4.9
2023-01-30T17:45:00.000-05:00
5.9
2023-01-30T18:00:00.000-05:00
6.9
2023-01-30T18:15:00.000-05:00
================================================================
The following query worked to select the desired json strings:
with exp_top as
( select s.value
from <source_table> c, c.values s
)
select s.value, s."dateTime" from exp_top c, c.value s;

Answer 1

Yes. You need to expand each array element into its own row. A recursive CTE (or something similar) will be needed to expand the arrays into rows. This can be done based on the max array length in the super or with some fixed set of numbers. This set of numbers will need to be crossed joined with your table to extract each array element.
I wrote up a similar answer previously - Extract value based on specific key from array of jsons in Amazon Redshift - take a look and see if this gets you unstuck. Let me know if you need help adapting this to your situation.
==============================================================
Based on the comments it looks like a more specific example is needed. This little test case should help you understand what is needed to make this work.
I've repeated your data a few times to create multiple rows and to populate the outer array with 2 inner arrays. This hopefully show how to unroll multiple nested arrays manually (the compact Redshift unrolling method is below but hard to understand if you don't get the concepts down first).
First set up the test data:
SET enable_case_sensitive_identifier TO true;
create table test1 (jvalues varchar(2048));
insert into test1 values
('[{"value":[{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T17:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T17:45:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:15:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:45:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:15:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:45:00.000-05:00"},{"value":"6.8","qualifiers":["P"],"dateTime":"2023-01-30T20:00:00.000-05:00"}]}, {"value":[{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T17:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T17:45:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:15:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:45:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:15:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:45:00.000-05:00"},{"value":"6.8","qualifiers":["P"],"dateTime":"2023-01-30T20:00:00.000-05:00"}]}]'),
('[{"value":[{"value":"5.9","qualifiers":["P"],"dateTime":"2023-01-30T17:30:00.000-05:00"},{"value":"5.9","qualifiers":["P"],"dateTime":"2023-01-30T17:45:00.000-05:00"},{"value":"8.9","qualifiers":["P"],"dateTime":"2023-01-30T18:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:15:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:45:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:15:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:45:00.000-05:00"},{"value":"6.8","qualifiers":["P"],"dateTime":"2023-01-30T20:00:00.000-05:00"}]}, {"value":[{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T17:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T17:45:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:15:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T18:45:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:00:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:15:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:30:00.000-05:00"},{"value":"6.9","qualifiers":["P"],"dateTime":"2023-01-30T19:45:00.000-05:00"},{"value":"6.8","qualifiers":["P"],"dateTime":"2023-01-30T20:00:00.000-05:00"}]}]');
create table test2 as select json_parse(jvalues) as svalues from test1;
Note that we have to turn on case sensitivity for the session to be able to select "dateTime" correctly.
Then unroll the arrays manually:
with recursive numbers(n) as
( select 0 as n
union all
select n + 1
from numbers n
where n.n < 20
),
exp_top as
( select row_number() over () as r, n as x, c.svalues[n].value
from test2 c
cross join numbers n
)
,
exp_bot as
( select r, x, n as y, c.value[n]
from exp_top c
cross join numbers n
where c.value is not null
)
select *, value.value as v, value."dateTime" as dt
from exp_bot
where value is not null;
This version
creates the numbers 0 - 19,
expands the outer array (2 elements in each row) by cross joining
with these numbers,
expands the inner array by the same method,
produces the desired results
Redshift has a built in method for doing this unrolling of super arrays and it is defined in the FROM clause. You can produce the same results from:
with exp_top as (select inx1, s.value from test2 c, c.svalues s at inx1)
select inx1, inx2, c.value[inx2] as value, s.value, s."dateTime" from exp_top c, c.value s at inx2;
Much more compact. This code has been tested and runs as is in Redshift. If you see the "dateTime" value as NULL it is likely that you don't have case sensitivity enabled.
==========================================================
To also have the original super column in the final result:
with exp_top as (select c.svalues, inx1, s.value from test2 c, c.svalues s at inx1)
select svalues, inx1, inx2, c.value[inx2] as value, s.value, s."dateTime" from exp_top c, c.value s at inx2;
==========================================================
I think that unrolling your actual data will be simpler than the code I provided for the general question.
First you don't need to use the test1 and test2 tables, you can query your table directly. If you still want to use test2 then use your table as the source of the "create table test2 ..." statement. But let's see if we can just use your source table.
with exp_top as (
select s.value from <your table> c, c.values s
)
select s.value, s."dateTime" from exp_top c, c.value s;
This code is untested but should work.