postgresql :: Operators invalid input syntax for type json

Question

I have some problems of postgresql .

select '123456' :: json and select 123456 ::json , all of the result is 123456 ; but select 'abc' :: json result is invalid input syntax for type json .

Is there some statement in official documents?

Answer 1

A JSON string must always be enclosed in double quotes:

SELECT '"abc"'::json;

I cannot find that explicitly mentioned in the PostgreSQL documentation, but it is clear that only a valid JSON can be cast to json.

The JSON specification documents this:

The representation of strings is similar to conventions used in the C family of programming languages. A string begins and ends with quotation marks.