Table 9.43 shows the operators that are available for use with the two JSON data types (see Section 8.14).
Table 9.43. json and jsonb Operators
| Operator | Right Operand Type | Description | Example | Example Result | 
|---|---|---|---|---|
| -> | int | Get JSON array element (indexed from zero, negative integers count from the end) | '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json->2 | {"c":"baz"} | 
| -> | text | Get JSON object field by key | '{"a": {"b":"foo"}}'::json->'a' | {"b":"foo"} | 
| ->> | int | Get JSON array element as text | '[1,2,3]'::json->>2 | 3 | 
| ->> | text | Get JSON object field as text | '{"a":1,"b":2}'::json->>'b' | 2 | 
| #> | text[] | Get JSON object at specified path | '{"a": {"b":{"c": "foo"}}}'::json#>'{a,b}' | {"c": "foo"} | 
| #>> | text[] | Get JSON object at specified path as text | '{"a":[1,2,3],"b":[4,5,6]}'::json#>>'{a,2}' | 3 | 
    There are parallel variants of these operators for both the
    json and jsonb types.
    The field/element/path extraction operators
    return the same type as their left-hand input (either json
    or jsonb), except for those specified as
    returning text, which coerce the value to text.
    The field/element/path extraction operators return NULL, rather than
    failing, if the JSON input does not have the right structure to match
    the request; for example if no such element exists.  The
    field/element/path extraction operators that accept integer JSON
    array subscripts all support negative subscripting from the end of
    arrays.
   
   The standard comparison operators shown in  Table 9.1 are available for
   jsonb, but not for json. They follow the
   ordering rules for B-tree operations outlined at Section 8.14.4.
  
   Some further operators also exist only for jsonb, as shown
   in Table 9.44.
   Many of these operators can be indexed by
   jsonb operator classes.  For a full description of
   jsonb containment and existence semantics, see Section 8.14.3.  Section 8.14.4
   describes how these operators can be used to effectively index
   jsonb data.
  
Table 9.44. Additional jsonb Operators
| Operator | Right Operand Type | Description | Example | 
|---|---|---|---|
| @> | jsonb | Does the left JSON value contain the right JSON path/value entries at the top level? | '{"a":1, "b":2}'::jsonb @> '{"b":2}'::jsonb | 
| <@ | jsonb | Are the left JSON path/value entries contained at the top level within the right JSON value? | '{"b":2}'::jsonb <@ '{"a":1, "b":2}'::jsonb | 
| ? | text | Does the string exist as a top-level key within the JSON value? | '{"a":1, "b":2}'::jsonb ? 'b' | 
| ?| | text[] | Do any of these array strings exist as top-level keys? | '{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'c'] | 
| ?& | text[] | Do all of these array strings exist as top-level keys? | '["a", "b"]'::jsonb ?& array['a', 'b'] | 
| || | jsonb | Concatenate two jsonbvalues into a newjsonbvalue | '["a", "b"]'::jsonb || '["c", "d"]'::jsonb | 
| - | text | Delete key/value pair or string element from left operand. Key/value pairs are matched based on their key value. | '{"a": "b"}'::jsonb - 'a'  | 
| - | text[] | Delete multiple key/value pairs or string elements from left operand. Key/value pairs are matched based on their key value. | '{"a": "b", "c": "d"}'::jsonb - '{a,c}'::text[]  | 
| - | integer | Delete the array element with specified index (Negative integers count from the end). Throws an error if top level container is not an array. | '["a", "b"]'::jsonb - 1  | 
| #- | text[] | Delete the field or element with specified path (for JSON arrays, negative integers count from the end) | '["a", {"b":1}]'::jsonb #- '{1,b}' | 
    The || operator concatenates the elements at the top level of
    each of its operands. It does not operate recursively. For example, if
    both operands are objects with a common key field name, the value of the
    field in the result will just be the value from the right hand operand.
   
   Table 9.45 shows the functions that are
   available for creating json and jsonb values.
   (There are no equivalent functions for jsonb, of the row_to_json
   and array_to_json functions. However, the to_jsonb
   function supplies much the same functionality as these functions would.)
  
Table 9.45. JSON Creation Functions
| Function | Description | Example | Example Result | 
|---|---|---|---|
| 
 
 | Returns the value as jsonorjsonb.
         Arrays and composites are converted
         (recursively) to arrays and objects; otherwise, if there is a cast
         from the type tojson, the cast function will be used to
         perform the conversion; otherwise, a scalar value is produced.
         For any scalar type other than a number, a Boolean, or a null value,
         the text representation will be used, in such a fashion that it is a
         validjsonorjsonbvalue. | to_json('Fred said "Hi."'::text) | "Fred said \"Hi.\"" | 
| array_to_json(anyarray [, pretty_bool]) | Returns the array as a JSON array. A PostgreSQL multidimensional array
         becomes a JSON array of arrays. Line feeds will be added between
         dimension-1 elements if pretty_boolis true. | array_to_json('{{1,5},{99,100}}'::int[]) | [[1,5],[99,100]] | 
| row_to_json(record [, pretty_bool]) | Returns the row as a JSON object. Line feeds will be added between
         level-1 elements if pretty_boolis true. | row_to_json(row(1,'foo')) | {"f1":1,"f2":"foo"} | 
| 
 
 | Builds a possibly-heterogeneously-typed JSON array out of a variadic argument list. | json_build_array(1,2,'3',4,5) | [1, 2, "3", 4, 5] | 
| 
 
 | Builds a JSON object out of a variadic argument list. By convention, the argument list consists of alternating keys and values. | json_build_object('foo',1,'bar',2) | {"foo": 1, "bar": 2} | 
| 
 
 | Builds a JSON object out of a text array. The array must have either exactly one dimension with an even number of members, in which case they are taken as alternating key/value pairs, or two dimensions such that each inner array has exactly two elements, which are taken as a key/value pair. | 
 
 | {"a": "1", "b": "def", "c": "3.5"} | 
| 
 
 | This form of json_objecttakes keys and values pairwise from two separate
         arrays. In all other respects it is identical to the one-argument form. | json_object('{a, b}', '{1,2}') | {"a": "1", "b": "2"} | 
     array_to_json and row_to_json have the same
     behavior as to_json except for offering a pretty-printing
     option.  The behavior described for to_json likewise applies
     to each individual value converted by the other JSON creation functions.
    
     The hstore extension has a cast
     from hstore to json, so that
     hstore values converted via the JSON creation functions
     will be represented as JSON objects, not as primitive string values.
    
   Table 9.46 shows the functions that
   are available for processing json and jsonb values.
  
Table 9.46. JSON Processing Functions
| Function | Return Type | Description | Example | Example Result | 
|---|---|---|---|---|
| 
 
 | int | Returns the number of elements in the outermost JSON array. | json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]') | 5 | 
| 
 
 | 
 
 | Expands the outermost JSON object into a set of key/value pairs. | select * from json_each('{"a":"foo", "b":"bar"}') | key | value -----+------- a | "foo" b | "bar" | 
| 
 
 | setof key text, value text | Expands the outermost JSON object into a set of key/value pairs. The
         returned values will be of type text. | select * from json_each_text('{"a":"foo", "b":"bar"}') | key | value -----+------- a | foo b | bar | 
| 
 
 | 
 
 | Returns JSON value pointed to by path_elems(equivalent to#>operator). | json_extract_path('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}','f4') | {"f5":99,"f6":"foo"} | 
| 
 
 | text | Returns JSON value pointed to by path_elemsastext(equivalent to#>>operator). | json_extract_path_text('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}','f4', 'f6') | foo | 
| 
 
 | setof text | Returns set of keys in the outermost JSON object. | json_object_keys('{"f1":"abc","f2":{"f3":"a", "f4":"b"}}') | json_object_keys ------------------ f1 f2 | 
| 
 
 | anyelement | Expands the object in from_jsonto a row
         whose columns match the record type defined bybase(see note below). | select * from json_populate_record(null::myrowtype, '{"a": 1, "b": ["2", "a b"], "c": {"d": 4, "e": "a  b c"}}') | 
 a |   b       |      c
---+-----------+-------------
 1 | {2,"a b"} | (4,"a b c")
 | 
| 
 
 | setof anyelement | Expands the outermost array of objects
         in from_jsonto a set of rows whose
         columns match the record type defined bybase(see
         note below). | select * from json_populate_recordset(null::myrowtype, '[{"a":1,"b":2},{"a":3,"b":4}]') | a | b ---+--- 1 | 2 3 | 4 | 
| 
 
 | 
 
 | Expands a JSON array to a set of JSON values. | select * from json_array_elements('[1,true, [2,false]]') | value ----------- 1 true [2,false] | 
| 
 
 | setof text | Expands a JSON array to a set of textvalues. | select * from json_array_elements_text('["foo", "bar"]') | value ----------- foo bar | 
| 
 
 | text | Returns the type of the outermost JSON value as a text string.
         Possible types are object,array,string,number,boolean, andnull. | json_typeof('-123.4') | number | 
| 
 
 | record | Builds an arbitrary record from a JSON object (see note below).  As
         with all functions returning record, the caller must
         explicitly define the structure of the record with anASclause. | select * from json_to_record('{"a":1,"b":[1,2,3],"c":[1,2,3],"e":"bar","r": {"a": 123, "b": "a b c"}}') as x(a int, b text, c int[], d text, r myrowtype)  | 
 a |    b    |    c    | d |       r
---+---------+---------+---+---------------
 1 | [1,2,3] | {1,2,3} |   | (123,"a b c")
 | 
| 
 
 | setof record | Builds an arbitrary set of records from a JSON array of objects (see
         note below).  As with all functions returning record, the
         caller must explicitly define the structure of the record with
         anASclause. | select * from json_to_recordset('[{"a":1,"b":"foo"},{"a":"2","c":"bar"}]') as x(a int, b text); | a | b ---+----- 1 | foo 2 | | 
| 
 
 | 
 
 | Returns from_jsonwith all object fields that have null values omitted. Other null values
         are untouched. | json_strip_nulls('[{"f1":1,"f2":null},2,null,3]') | [{"f1":1},2,null,3] | 
| 
 | 
 | Returns targetwith the section designated bypathreplaced bynew_value, or withnew_valueadded ifcreate_missingis true ( default istrue) and the item
         designated bypathdoes not exist.
         As with the path orientated operators, negative integers that
         appear inpathcount from the end
         of JSON arrays. | 
 
 | 
 
 | 
| 
 | 
 | Returns targetwithnew_valueinserted. Iftargetsection designated bypathis in a JSONB array,new_valuewill be inserted before target or
         after ifinsert_afteris true (default isfalse). Iftargetsection
         designated bypathis in JSONB object,new_valuewill be inserted only iftargetdoes not exist. As with the path
         orientated operators, negative integers that appear inpathcount from the end of JSON arrays. | 
 
 | 
 
 | 
| 
 | 
 | Returns from_jsonas indented JSON text. | jsonb_pretty('[{"f1":1,"f2":null},2,null,3]') | 
[
    {
        "f1": 1,
        "f2": null
    },
    2,
    null,
    3
]
 | 
      Many of these functions and operators will convert Unicode escapes in
      JSON strings to the appropriate single character.  This is a non-issue
      if the input is type jsonb, because the conversion was already
      done; but for json input, this may result in throwing an error,
      as noted in Section 8.14.
    
    The functions
    json[b]_populate_record,
    json[b]_populate_recordset,
    json[b]_to_record and
    json[b]_to_recordset
    operate on a JSON object, or array of objects, and extract the values
    associated with keys whose names match column names of the output row
    type.
    Object fields that do not correspond to any output column name are
    ignored, and output columns that do not match any object field will be
    filled with nulls.
    To convert a JSON value to the SQL type of an output column, the
    following rules are applied in sequence:
    
A JSON null value is converted to a SQL null in all cases.
       If the output column is of type json
       or jsonb, the JSON value is just reproduced exactly.
      
If the output column is a composite (row) type, and the JSON value is a JSON object, the fields of the object are converted to columns of the output row type by recursive application of these rules.
Likewise, if the output column is an array type and the JSON value is a JSON array, the elements of the JSON array are converted to elements of the output array by recursive application of these rules.
Otherwise, if the JSON value is a string literal, the contents of the string are fed to the input conversion function for the column's data type.
Otherwise, the ordinary text representation of the JSON value is fed to the input conversion function for the column's data type.
    While the examples for these functions use constants, the typical use
    would be to reference a table in the FROM clause
    and use one of its json or jsonb columns
    as an argument to the function.  Extracted key values can then be
    referenced in other parts of the query, like WHERE
    clauses and target lists.  Extracting multiple values in this
    way can improve performance over extracting them separately with
    per-key operators.
   
      All the items of the path parameter of jsonb_set
      as well as jsonb_insert except the last item must be present
      in the target. If create_missing is false, all
      items of the path parameter of jsonb_set must be
      present. If these conditions are not met the target is
      returned unchanged.
    
      If the last path item is an object key, it will be created if it
      is absent and given the new value. If the last path item is an array
      index, if it is positive the item to set is found by counting from
      the left, and if negative by counting from the right - -1
      designates the rightmost element, and so on.
      If the item is out of the range -array_length .. array_length -1,
      and create_missing is true, the new value is added at the beginning
      of the array if the item is negative, and at the end of the array if
      it is positive.
    
      The json_typeof function's null return value
      should not be confused with a SQL NULL.  While
      calling json_typeof('null'::json) will
      return null, calling json_typeof(NULL::json)
      will return a SQL NULL.
    
      If the argument to json_strip_nulls contains duplicate
      field names in any object, the result could be semantically somewhat
      different, depending on the order in which they occur. This is not an
      issue for jsonb_strip_nulls since jsonb values never have
      duplicate object field names.
    
    See also Section 9.20 for the aggregate
    function json_agg which aggregates record
    values as JSON, and the aggregate function
    json_object_agg which aggregates pairs of values
    into a JSON object, and their jsonb equivalents,
    jsonb_agg and jsonb_object_agg.