Paul Arterburn Paul Arterburn - 1 year ago 79
SQL Question

Sum all of the items in a JSONB array field

If my table is setup like:

id: 56789,
funding (JSONB): [
amount: 345678
amount: 7899

I can successfully sum the first amounts on every record with:

Rails —

SELECT SUM((funding->0->>'amount')::float) FROM "indicators"

How would you query a sum of all of the
(not just the 0 index items)?

Running Rails 5 & Postgres 9.5.4.

Note: This post is similar to How do I query using fields inside the new PostgreSQL JSON datatype? - but I'm looking for a way to iterate over each of the array elements to sum them (as opposed to calling them directly by an index number).

Thanks to @klin's answer below, I was able to put together the Rails version that gave me the aggregate total:

Indicator.joins("cross join lateral jsonb_array_elements(funding)").sum("(value->>'amount')::float")

Answer Source

Use jsonb_array_elements()

select sum((value->>'amount')::float)
from indicators
cross join lateral jsonb_array_elements(funding)
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