I have a column called "value" in my "answers" table.

|  value  |
|  [1,2]  |
|   [1]   |
| [1,2,3] |

The type of "value" is "jsonb".

I want to get the average value of each array in each row:

SELECT avg(value) AS avg_value
FROM answers

But this doesn't work because avg() is not a jsonb function. I've tried:

SELECT avg(value::integer[]) as avg_value
FROM answers

i.e. tried to cast the jsonb arrays into integer arrays and then taking the avg, but I get the following error: "cannot cast type jsonb to integer[]. null".

Any ideas?

1 Answer 1


You need to unnest the JSON array with jsonb_array_elements.

You can do this in a correlated subquery:

  (SELECT AVG(value::decimal(18,5))
   FROM jsonb_array_elements(value)
  ) AS avg_value
FROM answers;

DB Fiddle

  • Could you please explain what the decimal(18,5) does? Specifically the numbers 18 and 5.
    – user236222
    Jul 30, 2021 at 12:26
  • Precision and scale. I just picked anything, you could convert to decimal(5,2) if you like, or even float Jul 30, 2021 at 12:28
  • Thank you for your help!
    – user236222
    Jul 30, 2021 at 12:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.