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sqlarrayspostgresqlcoalescejsonb

Postgres coalesce to empty JSONB array

How can I coalesce a null column into an empty JSONB array? This doesn't work:

SELECT jsonb_array_elements(coalesce(null_column, '{}'::jsonb))
FROM table
WHERE id = 13;

-- ERROR:  cannot extract elements from an object

Neither this:

SELECT jsonb_array_elements(coalesce(null_column, '[]'::jsonb))
FROM table
WHERE id = 13;

-- ERROR:  cannot extract elements from a scalar
Solution

  • {} is an object but jsonb_array_elements expects an array, so replace {} with []

    Make sure that both arguments return a jsonb array. For example, if your column is an integer, you can use concat to add the square brackets and ::jsonb for the conversion

    SELECT jsonb_array_elements(coalesce(concat('[',my_column,']')::jsonb,'[]'::jsonb))