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Updated on 2024-05-21 GMT+08:00

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JSON/JSONB Functions and Operators

For details about the JSON/JSONB data type, see JSON/JSONB Types. For details about operators, see Table 1 and Table 2.

**Table 1** JSON/JSONB common operators
Operators	Left Operand Type	Right Operand Type	Return Type	Description	Example
->	Array-json(b)	int	json(b)	Obtains the array-json element. If the index does not exist, NULL is returned.	SELECT '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json->2; ?column? ------------- {"c":"baz"} (1 row)
->	object-json(b)	text	json(b)	Obtains the value by a key. If no record is found, NULL is returned.	SELECT '{"a": {"b":"foo"}}'::json->'a'; ?column? ------------- {"b":"foo"} (1 row)
->>	Array-json(b)	int	text	Obtains the JSON array element. If the subscript does not exist, NULL is returned.	SELECT '[1,2,3]'::json->>2; ?column? ---------- 3 (1 row)
->>	object-json(b)	text	text	Obtains the value by a key. If no record is found, NULL is returned.	SELECT '{"a":1,"b":2}'::json->>'b'; ?column? ---------- 2 (1 row)
#>	container-json (b)	text[]	json(b)	Obtains the JSON object in the specified path. If the path does not exist, NULL is returned.	SELECT '{"a": {"b":{"c": "foo"}}}'::json #>'{a,b}'; ?column? -------------- {"c": "foo"} (1 row)
#>>	container-json (b)	text[]	text	Obtains the JSON object in the specified path. If the path does not exist, NULL is returned.	SELECT '{"a":[1,2,3],"b":[4,5,6]}'::json #>>'{a,2}'; ?column? ---------- 3 (1 row)

For the #> and #>> operators, if no data can be found in the specified path, no error is reported and a NULL value is returned.

**Table 2** Additional JSONB support for operators
Operators	Right Operand Type	Description	Example
@>	jsonb	Specifies whether the top layer of the JSON on the left contains all items of the top layer of the JSON on the right.	'{"a":1, "b":2}'::jsonb @> '{"b":2}'::jsonb
<@	jsonb	Specifies whether all items in the JSON file on the left exist at the top layer of the JSON file on the right.	'{"b":2}'::jsonb <@ '{"a":1, "b":2}'::jsonb
?	text	Specifies whether the string of the key or element exists at the top layer of the JSON value.	'{"a":1, "b":2}'::jsonb ? 'b'
?\|	text[]	Specifies whether any of these array strings exists as top-layer keys.	'{"a":1, "b":2, "c":3}'::jsonb ?\| array['b', 'c']
?&	text[]	Specifies whether all these array strings exist as top-layer keys.	'["a", "b"]'::jsonb ?& array['a', 'b']
=	jsonb	Determines the size between two JSONB files, which is the same as the jsonb_eq function.	/
<>	jsonb	Determines the size between two JSONB files, which is the same as the jsonb_ne function.	/
<	jsonb	Determines the size between two JSONB files, which is the same as the jsonb_lt function.	/
>	jsonb	Determines the size between two JSONB files, which is the same as the jsonb_gt function.	/
<=	jsonb	Determines the size between two JSONB files, which is the same as the jsonb_le function.	/
>=	jsonb	Determines the size between two JSONB files, which is the same as the jsonb_ge function.	/

Functions Supported by JSON/JSONB

array_to_json(anyarray [, pretty_bool])
Description: Returns the array as JSON. It combines a multi-dimensional array into a JSON array. Line feeds will be added between one-dimensional elements if pretty_bool is true.

Return type: json
Example:
```
gaussdb=# SELECT array_to_json('{{1,5},{99,100}}'::int[]);
    array_to_json
    ------------------
    [[1,5],[99,100]]
    (1 row)
```

json_array_element(array-json, integer), jsonb_array_element(array-jsonb, integer)
Description: Same as the operator `->`, which returns the element with the specified subscript in the array.

Return type: json, jsonb
Example:
```
gaussdb=# SELECT json_array_element('[1,true,[1,[2,3
]],null]',2);
  json_array_element
  --------------------
  [1,[2,3]]
  (1 row)
```

json_array_element_text(array-json, integer), jsonb_array_element_text(array-jsonb, integer)
Description: Same as the operator `->>`, which returns the element with the specified subscript in the array.

Return type: text, text

Example:
```
gaussdb=# SELECT json_array_element_text('[1,true,[1,[2,3]],null]',2);
json_array_element_text
-----------------------
  [1,[2,3]]
  (1 row)
```

json_object_field(object-json, text), jsonb_object_field(object-jsonb, text)
Description: Same as the operator `->`, which returns the value of a specified key in an object.

Return type: json, json
Example:
```
 gaussdb=# SELECT json_object_field('{"a": {"b":"foo"}}','a');
  json_object_field
  -------------------
  {"b":"foo"}
  (1 row)
```
json_object_field_text(object-json, text), jsonb_object_field_text(object-jsonb, text)
Description: Same as the operator `->`, which returns the value of a specified key in an object.

Return type: text, text
Example:
```
 gaussdb=# SELECT json_object_field_text('{"a": {"b":"foo"}}','a');
  json_object_field_text
  ----------------------
  {"b":"foo"}
  (1 row)
```

json_extract_path(json, VARIADIC text[]), jsonb_extract_path((jsonb, VARIADIC text[])
Description: Equivalent to the operator `#>` searches for JSON based on the path specified by $2 and returns the result.

Return type: json, jsonb
Example:
```
 gaussdb=# SELECT json_extract_path('{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}', 'f4','f6');
   json_extract_path
  -------------------
   "stringy"
  (1 row)
```

json_extract_path_op(json, text[]), jsonb_extract_path_op(jsonb, text[])
Description: Same as the operator `#>` and searches for JSON based on the path specified by $2 and returns the result.

Return type: json, jsonb
Example:
```
  gaussdb=# SELECT json_extract_path_op('{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}', ARRAY['f4','f6']);
   json_extract_path_op
  ---------------------
   "stringy"
  (1 row)
```

json_extract_path_text(json, VARIADIC text[]), jsonb_extract_path_text((jsonb, VARIADIC text[])
Description: Same as the operator `#>` and searches for JSON based on the path specified by $2 and returns the result.

Return type: text, text
Example:
```
 gaussdb=# SELECT json_extract_path_text('{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}', 'f4','f6');
   json_extract_path_text
  -----------------------
   "stringy"
  (1 row)
```

json_extract_path_text_op(json, text[]), jsonb_extract_path_text_op(jsonb, text[])
Description: Same as the operator `#>>` and searches for JSON based on the path specified by $2 and returns the result.

Return type: text, text
Example:
```
 gaussdb=# SELECT json_extract_path_text_op('{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}', ARRAY['f4','f6']);
   json_extract_path_text_op
  --------------------------
   "stringy"
  (1 row)
```

json_array_elements(array-json), jsonb_array_elements(array-jsonb)

Description: Splits an array. Each element returns a row.

Return type: json, jsonb

Example:

 gaussdb=# SELECT json_array_elements('[1,true,[1,[2,3]],null]');
   json_array_elements
  ---------------------
   1
   true
   [1,[2,3]]
   null
  (4 rows)

json_array_elements_text(array-json), jsonb_array_elements_text(array-jsonb)
Description: Splits an array. Each element returns a row.

Return type: text, text
Example:
```
gaussdb=# SELECT * FROM  json_array_elements_text('[1,true,[1,[2,3]],null]');
     value
  -----------
   1
   true
   [1,[2,3]]

  (4 rows)
```

json_array_length(array-json), jsonb_array_length(array-jsonb)

Description: Returns the array length.

Return type: integer

Example:

  gaussdb=# SELECT json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4,null]');
   json_array_length
  -------------------
                   6
  (1 row)

json_each(object-json), jsonb_each(object-jsonb)
Description: Splits each key-value pair of an object into one row and two columns.

Return type: setof(key text, value json), setof(key text, value jsonb)
Example:
```
 gaussdb=# SELECT * FROM  json_each('{"f1":[1,2,3],"f2":{"f3":1},"f4":null}');
   key |  value
  -----+----------
   f1  | [1,2,3]
   f2  | {"f3":1}
   f4  | null
  (3 rows)
```

json_each_text(object-json), jsonb_each_text(object-jsonb)
Description: Splits each key-value pair of an object into one row and two columns.

Return type: setof(key text, value text), setof(key text, value text)
Example:
```
 gaussdb=# SELECT * FROM  json_each_text('{"f1":[1,2,3],"f2":{"f3":1},"f4":null}');
   key |  value
  -----+----------
   f1  | [1,2,3]
   f2  | {"f3":1}
   f4  |
  (3 rows)
```

json_object_keys(object-json), jsonb_object_keys(object-jsonb)

Description: Returns all keys at the top layer of the object.

Return type: SETOF text

Example:

  gaussdb=# SELECT json_object_keys('{"f1":"abc","f2":{"f3":"a", "f4":"b"}, "f1":"abcd"}');
   json_object_keys
  ------------------
   f1
   f2
   f1
  (3 rows)

JSONB deduplication operations:

  gaussdb=# SELECT jsonb_object_keys('{"f1":"abc","f2":{"f3":"a", "f4":"b"}, "f1":"abcd"}');
   jsonb_object_keys
  -------------------
   f1
   f2
  (2 rows)

json_typeof(json), jsonb_typeof(jsonb)

Description: Checks the JSON type.

Return type: text, text

Example:

 gaussdb=# SELECT value, json_typeof(value) FROM (values (json '123.4'), (json '"foo"'), (json 'true'), (json 'null'), (json '[1, 2, 3]'), (json '{"x":"foo", "y":123}'), (NULL::json))  AS data(value);
          value         | json_typeof
  ----------------------+-------------
   123.4                | number
   "foo"                | string
   true                 | boolean
   null                 | null
   [1, 2, 3]            | array
   {"x":"foo", "y":123} | object
                        |
  (7 rows)

json_build_array( [VARIADIC "any"] )

Description: Constructs a JSON array from a variable parameter list.

Return type: array-json

Example:

 gaussdb=# SELECT json_build_array('a',1,'b',1.2,'c',true,'d',null,'e',json '{"x": 3, "y": [1,2,3]}','');
                               json_build_array
  ---------------------------------------------------------------------------
   ["a", 1, "b", 1.2, "c", true, "d", null, "e", {"x": 3, "y": [1,2,3]}, ""]
  (1 row)

json_build_object( [VARIADIC "any"] )
Description: Constructs a JSON object from a variable parameter list. The number of input parameters must be an even number. Every two input parameters form a key-value pair. Note that the value of a key cannot be null.

Return type: object-json
Example:
```
 gaussdb=# SELECT json_build_object(1,2);
   json_build_object
  -------------------
   {"1" : 2}
  (1 row)
```

json_object(text[]), json_object(text[], text[])
Description: Constructs an object-json from a text array. This is an overloaded function. When the input parameter is a text array, the array length must be an even number, and members are considered as alternate key-value pairs. When two text arrays are used, the first array is considered as a key, and the second array a value. The lengths of the two arrays must be the same. Note that the value of a key cannot be null.

Return type: object-json
Example:
```
gaussdb=# SELECT json_object('{a,1,b,2,3,NULL,"d e f","a b c"}');
                        json_object
  -------------------------------------------------------
   {"a" : "1", "b" : "2", "3" : null, "d e f" : "a b c"}
  (1 row)
```
```
  gaussdb=# SELECT json_object('{a,b,"a b c"}', '{a,1,1}');
                json_object
  ---------------------------------------
   {"a" : "a", "b" : "1", "a b c" : "1"}
  (1 row)
```

json_agg(any)

Description: Aggregates values into a JSON array.

Return type: array-json

Example:

 gaussdb=# SELECT * FROM classes;
  name | score
  -----+-------
  A    |     2
  A    |     3
  D    |     5
  D    |
  (4 rows)

  gaussdb=# SELECT name, json_agg(score) score FROM classes GROUP BY name ORDER BY name;
  name |      score
  -----+-----------------
  A    | [2, 3]
  D    | [5, null]
       | [null]
  (3 rows)

json_object_agg(any, any)

Description: Aggregates values into a JSON object.

Return type: object-json

Example:

  gaussdb=# SELECT * FROM classes;
  name | score
  -----+-------
  A    |     2
  A    |     3
  D    |     5
  D    |
  (4 rows)

  gaussdb=# SELECT json_object_agg(name, score) FROM classes GROUP BY name ORDER BY name;
       json_object_agg
  -------------------------
   { "A" : 2, "A" : 3 }
   { "D" : 5, "D" : null }
  (2 rows)

- jsonb_contained(jsonb, jsonb)
Description: Same as the operator `<@`, determines whether all elements in $1 exist at the top layer of $2.

Return type: Boolean
Example:
```
 gaussdb=# SELECT jsonb_contained('[1,2,3]', '[1,2,3,4]');
   jsonb_contained
  -----------------
   t
  (1 row)
```

- jsonb_contains(jsonb, jsonb)
Description: Same as the operator `@>`, checks whether all top-layer elements in $1 are contained in $2.

Return type: Boolean
Example:
```
 gaussdb=# SELECT jsonb_contains('[1,2,3,4]', '[1,2,3]');
   jsonb_contains
  ----------------
   t
  (1 row)
```

- jsonb_exists(jsonb, text)
Description: Same as the operator `?`, determines whether all elements in the string array $2 exist at the top layer of $1 in the form of key\elem\scalar.

Return type: Boolean
Example:
```
  gaussdb=# SELECT jsonb_exists('["1",2,3]', '1');
   jsonb_exists
  --------------
   t
  (1 row)
```

- jsonb_exists_all(jsonb, text[])
Description: Same as the operator `?&`, checks whether all elements in the string array $2 exist at the top layer of $1 in the form of key\elem\scalar.

Return type: Boolean
Example:
```
  gaussdb=# SELECT jsonb_exists_all('["1","2",3]', '{1, 2}');
   jsonb_exists_all
  ------------------
   t
  (1 row)
```

- jsonb_exists_any(jsonb, text[])
Description: Same as the operator `?|`, checks whether all elements in the string array $2 exist at the top layer of $1 in the form of key\elem\scalar.

Return type: Boolean
Example:
```
  gaussdb=# SELECT jsonb_exists_any('["1","2",3]', '{1, 2, 4}');
   jsonb_exists_any
  ------------------
   t
  (1 row)
```

- jsonb_cmp(jsonb, jsonb)
Description: Compares values. A positive value indicates greater than, a negative value indicates less than, and 0 indicates equal.

Return type: integer
Example:
```
gaussdb=# SELECT jsonb_cmp('["a", "b"]', '{"a":1, "b":2}');
   jsonb_cmp
  -----------
          -1
  (1 row)
```

- jsonb_eq(jsonb, jsonb)
Description: Same as the operator `=`, compares two values.

Return type: Boolean
Example:
```
  gaussdb=# SELECT jsonb_eq('["a", "b"]', '{"a":1, "b":2}');
   jsonb_eq
  ----------
   f
  (1 row)
```

- jsonb_ne(jsonb, jsonb)
Description: Same as the operator `<>`, compares two values.

Return type: Boolean
Example:
```
  gaussdb=# SELECT jsonb_ne('["a", "b"]', '{"a":1, "b":2}');
   jsonb_ne
  ----------
   t
  (1 row)
```

- jsonb_gt(jsonb, jsonb)
Description: Same as the operator `>`, compares two values.

Return type: Boolean

Example:
```
 gaussdb=# SELECT jsonb_gt('["a", "b"]', '{"a":1, "b":2}');
   jsonb_gt
  ----------
   f
  (1 row)
```

- jsonb_ge(jsonb, jsonb)
Description: Same as the operator `>=`, compares two values.

Return type: Boolean
Example:
```
 gaussdb=# SELECT jsonb_ge('["a", "b"]', '{"a":1, "b":2}');
   jsonb_ge
  ----------
   f
  (1 row)
```

- jsonb_lt(jsonb, jsonb)
Description: Same as the operator `<`, compares two values.

Return type: Boolean
Example:
```
 gaussdb=# SELECT jsonb_lt('["a", "b"]', '{"a":1, "b":2}');
   jsonb_lt
  ----------
   t
  (1 row)
```

- jsonb_le(jsonb, jsonb)
Description: Same as the operator `<=`, compares two values.

Return type: Boolean
Example:
```
 gaussdb=# SELECT jsonb_le('["a", "b"]', '{"a":1, "b":2}');
   jsonb_le
  ----------
   t
  (1 row)
```

- to_json(anyelement)

Description: Converts parameters to `json`.

Return type: json

Example:

 gaussdb=# SELECT to_json('{1,5}'::text[]);
    to_json
  -----------
   ["1","5"]
  (1 row)

- jsonb_hash(jsonb)
Description: Performs the hash operation on JSONB.

Return type: integer

Example:
```
 gaussdb=# SELECT jsonb_hash('[1,2,3]');
 jsonb_hash
------------
 -559968547
(1 row)
```

Other functions

 json_agg_transfn
 json_agg_finalfn
 json_object_agg_transfn
 json_object_agg_finalfn

Parent topic: Functions and Operators

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Next topic: HLL Functions and Operators

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