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I came across this question on how to update nth element of array, but it has nested json values in it instead of a plain array of strings.

Here are some sample json values from jsonb column of the table.

{"pattern": {"values": ["foo", "edfgh"]}}
{"pattern": {"values": ["abc", "abdhi", "foo"]}}
{"pattern": {"values": ["these", "abcd", "para", "avil"]}}

We can select the nth element using

select data #> '{pattern, values, 0}' from table;

How can we loop through array and update foo to bar if it is present in that array?

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  • Json values are not valid please correct that Commented Apr 24, 2019 at 20:24
  • @SahapAsci Corrected it. Thanks. Commented Apr 25, 2019 at 7:04
  • Copy of dba.stackexchange.com/questions/193390/… Commented Apr 25, 2019 at 7:21
  • @A.J.Alger The question is not the same. The value foo can be anywhere in array. Commented Apr 25, 2019 at 9:13
  • how about if there is more than one "foo" in the array ? Commented Apr 29, 2019 at 10:54

1 Answer 1

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You can use a query like the one below;

UPDATE table SET
  data = jsonb_set(data,'{pattern, values}', ((data->'pattern'->'values') - 'foo') ||  '["bar"]' )
WHERE
  (data #> '{pattern, values}') ? 'foo';

Details;

First you have to find records which have "foo" value in "values" array;

(data #> '{pattern, values}') ? 'foo'

After that remove the value "foo" from the array;

((data->'pattern'->'values') - 'foo')

Create a new array by concatenating your new value(s).

((data->'pattern'->'values') - 'foo') ||  '["bar"]'

Replace new array with the old one.

jsonb_set(data,'{pattern, values}', new_array)
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  • This replaces the element but doesn't preserve the order. Is there a way to update it and preserve order also? Commented Apr 26, 2019 at 4:28

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