Using substring to get a JSON value in PostgreSQL

Question

I've got a table field "data" with the following json:

[{"reason": "Other", "bla": 12345, "amount": "34.00", "moredata": [23, 22], "date": "2014-01-02T01:55:28.646364+00:00", "message": "Bla", "applied_to": "client"}]

And I'd like to get only the value of the json value of amount, so 34.00 in the case above in PostgreSQL.

So far I have:

substring(data from '%#"_amount_: ___.___#"%' for '#'),

Sadly this gives me "amount":"34.00", instead of just 34.00. It also doesn't work if the amount value is 9.00 or 102.00.

Any help would be appreciated.

Answer 1

Try:

substring(data from '(?:"amount": ")([\d\.]*)')

See it working here and here 's what it does:

 NODE EXPLANATION -------------------------------------------------------------------- (?: group, but do not capture: -------------------------------------------------------------------- "amount": " '"amount": "' -------------------------------------------------------------------- ) end of grouping -------------------------------------------------------------------- ( group and capture to \\1: -------------------------------------------------------------------- [\\d\\.]* any character of: digits (0-9), '\\.' (0 or more times (matching the most amount possible)) -------------------------------------------------------------------- ) end of \\1