JSON/JSONB Functions and Operators

For details about the JSON/JSONB data type, see JSON/JSONB Types.

Table 1 JSON/JSONB common operators

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

CAUTION: 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

Operator	Right Operand Type	Description	Example
@>	jsonb	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	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	Whether the string of the key or element exists at the top layer of the JSON value.	'{"a":1, "b":2}'::jsonb ? 'b'
?|	text[]	Whether any of these array strings exists as top-layer keys.	'{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'c']
?&	text[]	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 an array as JSON. A multi-dimensional array becomes a JSON array of arrays. If the value of pretty_bool is true, a newline character is added between one-dimensional elements.

  Return type: json

  For example:

  MogDB=# SELECT array_to_json('{{1,5},{99,100}}'::int[]);
      array_to_json
      ------------------
      [[1,5],[99,100]]
      (1 row)

• row_to_json(record [, pretty_bool])

  Description: Returns a row as JSON. If the value of preretty_bool is true, a newline character is added between one-dimensional elements.

  Return type: json

  For example:

  MogDB=# SELECT row_to_json(row(1,'foo'));
           row_to_json
      ---------------------
       {"f1":1,"f2":"foo"}    (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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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 #>, searches for JSON based on the path specified by $2 and returns the result.

  Return type: json, jsonb

  For example:

  MogDB=# select json_extract_path_op('{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}', '{f4,f6}');
    json_extract_path_op
   ---------------------
    "stringy"
   (1 row)

• json_extract_path_text(json, VARIADIC text[]), jsonb_extract_path_text((jsonb, VARIADIC text[])

  Description: Equivalent to the operator #>, searches for JSON based on the path specified by $2 and return the result.

  Return type: text, text

  For example:

  MogDB=# 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 #>, searches for JSON based on the path specified by $2 and returns the result.

  Return type: text, text

  For example:

  MogDB=# select json_extract_path_text_op('{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}', '{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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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)

  For example:

  MogDB=# 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)

  For example:

  MogDB=# 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

  For example:

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

• JSONB deduplication operations:

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

• json_populate_record(anyelement, object-json [, bool]), jsonb_populate_record(anyelement, object-jsonb [, bool])

  Description: $1 must be a compound parameter. Each key-value in the object-json file is split. The key is used as the column name to match the column name in $1 and fill in the $1 format.

  Return type: anyelement, anyelement

  For example:

  MogDB=# create type jpop as (a text, b int, c bool);
   CREATE TYPE
   postgres=# select * from json_populate_record(null::jpop,'{"a":"blurfl","x":43.2}');
      a    | b | c
   --------+---+---
    blurfl |   |
   (1 row)

  MogDB=# select * from json_populate_record((1,1,null)::jpop,'{"a":"blurfl","x":43.2}');
       a    | b | c
    --------+---+---
     blurfl | 1 |
    (1 row)

• json_populate_record_set(anyelement, array-json [, bool]), jsonb_populate_record_set(anyelement, array-jsonb [, bool])

  Description: Performs the preceding operations on each element in the $2 array by referring to the json_populate_record and jsonb_populate_record functions. Therefore, each element in the $2 array must be of the object-json type.

  Return type: setof anyelement, setof anyelement

  For example:

  MogDB=# create type jpop as (a text, b int, c bool);
   CREATE TYPE
   postgres=# select * from json_populate_recordset(null::jpop, '[{"a":1,"b":2},{"a":3,"b":4}]');
    a | b | c
   ---+---+---
    1 | 2 |
    3 | 4 |
   (2 rows)

• json_typeof(json), jsonb_typeof(jsonb)

  Description: Checks the JSON type.

  Return type: text, text

  For example:

  MogDB=# select value, json_typeof(value)
   postgres-# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# select json_build_object(1,2);
    json_build_object
   -------------------
    {"1" : 2}
   (1 row)

• json_to_record(object-json, bool)

  Description: Like all functions that return record, the caller must explicitly define the structure of the record with an AS clause. The key-value pair of object-json is split and reassembled. The key is used as a column name to match and fill in the structure of the specified record.

  Return type: record

  For example:

  MogDB=# select * from json_to_record('{"a":1,"b":"foo","c":"bar"}',true) as x(a int, b text, d text);
     a |  b  | d
    ---+-----+---
     1 | foo |
    (1 row)

• json_to_recordset(array-json, bool)

  Description: Executes the preceding function on each element in the array by referring to thejson_to_record function. Therefore, each element in the array must be object-json.

  Return type: SETOF record

  For example:

  MogDB=# select * from json_to_recordset(
  mogdb(#   '[{"a":1,"b":"foo","d":false},{"a":2,"b":"bar","c":true}]',
  mogdb(#   false
  mogdb(# ) as x(a int, b text, c boolean);
    a |  b  | c
   ---+-----+---
    1 | foo |
    2 | bar | t
   (2 rows)

• 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

  For example:

  MogDB=# 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)

  MogDB=# 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

  For example:

  MogDB=# select * from classes;
   name | score
   -----+-------
   A    |     2
   A    |     3
   D    |     5
   D    |
   (4 rows)

  MogDB=# 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

  For example:

  MogDB=# select * from classes;
   name | score
   -----+-------
   A    |     2
   A    |     3
   D    |     5
   D    |
   (4 rows)

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

  MogDB=# 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

  For example:

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