Contents
json_typeof()
A function returning the type of a json value as a string
json_typeof() is a system function returning the type of the top-level json value as a text string.
json_typeof() was added in PostgreSQL 9.4.
Usage
json_typeof (json) →text
One of the following values will be returned:
objectarraystringnumberbooleannull
Note that these values, particularly in the case of null, are not direct equivalents of the corresponding SQL data types.
Change history
- PostgreSQL 9.4
- added (commit 4d212bac)
Examples
Using json_typeof() to determine the type of various json values:
postgres=# SELECT json_typeof('{"foo":[]}'::json);
json_typeof
-------------
object
(1 row)
postgres=# SELECT json_typeof('[]'::json);
json_typeof
-------------
array
(1 row)
postgres=# SELECT json_typeof('"foo"'::json);
json_typeof
-------------
string
(1 row)
postgres=# SELECT json_typeof('123'::json);
json_typeof
-------------
number
(1 row)
postgres=# SELECT json_typeof('false'::json);
json_typeof
-------------
boolean
(1 row)
postgres=# SELECT json_typeof('null'::json);
json_typeof
-------------
null
(1 row)
Note that any numeric value maps to a number type:
postgres=# SELECT json_typeof(123::int::text::json); json_typeof ------------- number (1 row) postgres=# SELECT json_typeof(1.23::numeric::text::json); json_typeof ------------- number (1 row)
A json null is not equivalent to an SQL NULL:
postgres=# SELECT json_typeof('null'::json),
json_typeof(NULL::json) IS NULL;
json_typeof | ?column?
-------------+----------
null | t
(1 row)
References
- PostgreSQL documentation: JSON Processing Functions