This section describes:
functions and operators for processing and creating JSON data
the SQL/JSON path language
To learn more about the SQL/JSON standard, see [sqltr-19075-6]. For details on JSON types supported in PostgreSQL, see Section 8.14.
Table 9.44 shows the operators that are available for use with JSON data types (see Section 8.14).
Table 9.44. json and jsonb Operators
| Operator | Right Operand Type | Return type | Description | Example | Example Result | 
|---|---|---|---|---|---|
| -> | int | jsonorjsonb | Get JSON array element (indexed from zero, negative integers count from the end) | '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json->2 | {"c":"baz"} | 
| -> | text | jsonorjsonb | Get JSON object field by key | '{"a": {"b":"foo"}}'::json->'a' | {"b":"foo"} | 
| ->> | int | text | Get JSON array element as text | '[1,2,3]'::json->>2 | 3 | 
| ->> | text | text | Get JSON object field as text | '{"a":1,"b":2}'::json->>'b' | 2 | 
| #> | text[] | jsonorjsonb | Get JSON object at the specified path | '{"a": {"b":{"c": "foo"}}}'::json#>'{a,b}' | {"c": "foo"} | 
| #>> | text[] | text | Get JSON object at the 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 9.45.
   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 9.45. 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}' | 
| @? | jsonpath | Does JSON path return any item for the specified JSON value? | '{"a":[1,2,3,4,5]}'::jsonb @? '$.a[*] ? (@ > 2)' | 
| @@ | jsonpath | Returns the result of JSON path predicate check for the specified JSON value.
        Only the first item of the result is taken into account.  If the
        result is not Boolean, then nullis returned. | '{"a":[1,2,3,4,5]}'::jsonb @@ '$.a[*] > 2' | 
    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.
   
    The @? and @@ operators suppress
    the following errors: lacking object field or array element, unexpected
    JSON item type, and numeric errors.
    This behavior might be helpful while searching over JSON document
    collections of varying structure.
   
   Table 9.46 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 9.46. 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 9.47 shows the functions that
   are available for processing json and jsonb values.
  
Table 9.47. 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 oriented 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
         oriented 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
]
 | 
| 
 | boolean | Checks whether JSON path returns any item for the specified JSON value. | 
 | 
 | 
| 
 | boolean | Returns the result of JSON path predicate check for the specified JSON value.
          Only the first item of the result is taken into account.  If the
          result is not Boolean, then nullis returned. | 
 | 
 | 
| 
 | setof jsonb | Gets all JSON items returned by JSON path for the specified JSON value. | 
 | 
 jsonb_path_query ------------------ 2 3 4 
 | 
| 
 | jsonb | Gets all JSON items returned by JSON path for the specified JSON value and wraps result into an array. | 
 | 
 | 
| 
 | jsonb | Gets the first JSON item returned by JSON path for the specified JSON
          value.  Returns NULLon no results. | 
 | 
 | 
      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.
    
    The jsonb_path_exists, jsonb_path_match,
    jsonb_path_query, jsonb_path_query_array, and
    jsonb_path_query_first
    functions have optional vars and silent
    arguments.
   
    If the vars argument is specified, it provides an
    object containing named variables to be substituted into a
    jsonpath expression.
   
    If the silent argument is specified and has the
    true value, these functions suppress the same errors
    as the @? and @@ operators.
   
    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.
  
   SQL/JSON path expressions specify the items to be retrieved
   from the JSON data, similar to XPath expressions used
   for SQL access to XML. In PostgreSQL,
   path expressions are implemented as the jsonpath
   data type and can use any elements described in
   Section 8.14.6.
  
JSON query functions and operators pass the provided path expression to the path engine for evaluation. If the expression matches the queried JSON data, the corresponding SQL/JSON item is returned. Path expressions are written in the SQL/JSON path language and can also include arithmetic expressions and functions. Query functions treat the provided expression as a text string, so it must be enclosed in single quotes.
   A path expression consists of a sequence of elements allowed
   by the jsonpath data type.
   The path expression is evaluated from left to right, but
   you can use parentheses to change the order of operations.
   If the evaluation is successful, a sequence of SQL/JSON items
   (SQL/JSON sequence) is produced,
   and the evaluation result is returned to the JSON query function
   that completes the specified computation.
  
   To refer to the JSON data to be queried (the
   context item), use the $ sign
   in the path expression. It can be followed by one or more
   accessor operators,
   which go down the JSON structure level by level to retrieve the
   content of context item. Each operator that follows deals with the
   result of the previous evaluation step.
  
For example, suppose you have some JSON data from a GPS tracker that you would like to parse, such as:
{
  "track": {
    "segments": [
      {
        "location":   [ 47.763, 13.4034 ],
        "start time": "2018-10-14 10:05:14",
        "HR": 73
      },
      {
        "location":   [ 47.706, 13.2635 ],
        "start time": "2018-10-14 10:39:21",
        "HR": 135
      }
    ]
  }
}
   To retrieve the available track segments, you need to use the
   . accessor
   operator for all the preceding JSON objects:
key
'$.track.segments'
   If the item to retrieve is an element of an array, you have
   to unnest this array using the [*] operator. For example,
   the following path will return location coordinates for all
   the available track segments:
'$.track.segments[*].location'
   To return the coordinates of the first segment only, you can
   specify the corresponding subscript in the []
   accessor operator. Note that the SQL/JSON arrays are 0-relative:
'$.track.segments[0].location'
   The result of each path evaluation step can be processed
   by one or more jsonpath operators and methods
   listed in Section 9.15.2.3.
   Each method name must be preceded by a dot. For example,
   you can get an array size:
'$.track.segments.size()'
   For more examples of using jsonpath operators
   and methods within path expressions, see
   Section 9.15.2.3.
  
   When defining the path, you can also use one or more
   filter expressions that work similar to the
   WHERE clause in SQL. A filter expression begins with
   a question mark and provides a condition in parentheses:
? (condition)
   Filter expressions must be specified right after the path evaluation step
   to which they are applied. The result of this step is filtered to include
   only those items that satisfy the provided condition. SQL/JSON defines
   three-valued logic, so the condition can be true, false,
   or unknown. The unknown value
   plays the same role as SQL NULL and can be tested
   for with the is unknown predicate. Further path
   evaluation steps use only those items for which filter expressions
   return true.
  
   Functions and operators that can be used in filter expressions are listed
   in Table 9.49. The path
   evaluation result to be filtered is denoted by the @
   variable. To refer to a JSON element stored at a lower nesting level,
   add one or more accessor operators after @.
  
Suppose you would like to retrieve all heart rate values higher than 130. You can achieve this using the following expression:
'$.track.segments[*].HR ? (@ > 130)'
To get the start time of segments with such values instead, you have to filter out irrelevant segments before returning the start time, so the filter expression is applied to the previous step, and the path used in the condition is different:
'$.track.segments[*] ? (@.HR > 130)."start time"'
You can use several filter expressions on the same nesting level, if required. For example, the following expression selects all segments that contain locations with relevant coordinates and high heart rate values:
'$.track.segments[*] ? (@.location[1] < 13.4) ? (@.HR > 130)."start time"'
Using filter expressions at different nesting levels is also allowed. The following example first filters all segments by location, and then returns high heart rate values for these segments, if available:
'$.track.segments[*] ? (@.location[1] < 13.4).HR ? (@ > 130)'
You can also nest filter expressions within each other:
'$.track ? (exists(@.segments[*] ? (@.HR > 130))).segments.size()'
This expression returns the size of the track if it contains any segments with high heart rate values, or an empty sequence otherwise.
PostgreSQL's implementation of SQL/JSON path language has the following deviations from the SQL/JSON standard:
     .datetime() item method is not implemented yet
     mainly because immutable jsonpath functions and operators
     cannot reference session timezone, which is used in some datetime
     operations.  Datetime support will be added to jsonpath
     in future versions of PostgreSQL.
    
     A path expression can be a Boolean predicate, although the SQL/JSON
     standard allows predicates only in filters.  This is necessary for
     implementation of the @@ operator. For example,
     the following jsonpath expression is valid in
     PostgreSQL:
'$.track.segments[*].HR < 70'
     There are minor differences in the interpretation of regular
     expression patterns used in like_regex filters, as
     described in Section 9.15.2.2.
    
When you query JSON data, the path expression may not match the actual JSON data structure. An attempt to access a non-existent member of an object or element of an array results in a structural error. SQL/JSON path expressions have two modes of handling structural errors:
lax (default) — the path engine implicitly adapts the queried data to the specified path. Any remaining structural errors are suppressed and converted to empty SQL/JSON sequences.
strict — if a structural error occurs, an error is raised.
The lax mode facilitates matching of a JSON document structure and path expression if the JSON data does not conform to the expected schema. If an operand does not match the requirements of a particular operation, it can be automatically wrapped as an SQL/JSON array or unwrapped by converting its elements into an SQL/JSON sequence before performing this operation. Besides, comparison operators automatically unwrap their operands in the lax mode, so you can compare SQL/JSON arrays out-of-the-box. An array of size 1 is considered equal to its sole element. Automatic unwrapping is not performed only when:
       The path expression contains type() or
       size() methods that return the type
       and the number of elements in the array, respectively.
      
The queried JSON data contain nested arrays. In this case, only the outermost array is unwrapped, while all the inner arrays remain unchanged. Thus, implicit unwrapping can only go one level down within each path evaluation step.
For example, when querying the GPS data listed above, you can abstract from the fact that it stores an array of segments when using the lax mode:
'lax $.track.segments.location'
    In the strict mode, the specified path must exactly match the structure of
    the queried JSON document to return an SQL/JSON item, so using this
    path expression will cause an error. To get the same result as in
    the lax mode, you have to explicitly unwrap the
    segments array:
'strict $.track.segments[*].location'
     SQL/JSON path expressions allow matching text to a regular expression
     with the like_regex filter.  For example, the
     following SQL/JSON path query would case-insensitively match all
     strings in an array that start with an English vowel:
'$[*] ? (@ like_regex "^[aeiou]" flag "i")'
     The optional flag string may include one or more of
     the characters
     i for case-insensitive match,
     m to allow ^
     and $ to match at newlines,
     s to allow . to match a newline,
     and q to quote the whole pattern (reducing the
     behavior to a simple substring match).
    
     The SQL/JSON standard borrows its definition for regular expressions
     from the LIKE_REGEX operator, which in turn uses the
     XQuery standard.  PostgreSQL does not currently support the
     LIKE_REGEX operator.  Therefore,
     the like_regex filter is implemented using the
     POSIX regular expression engine described in
     Section 9.7.3.  This leads to various minor
     discrepancies from standard SQL/JSON behavior, which are cataloged in
     Section 9.7.3.8.
     Note, however, that the flag-letter incompatibilities described there
     do not apply to SQL/JSON, as it translates the XQuery flag letters to
     match what the POSIX engine expects.
    
     Keep in mind that the pattern argument of like_regex
     is a JSON path string literal, written according to the rules given in
     Section 8.14.6.  This means in particular that any
     backslashes you want to use in the regular expression must be doubled.
     For example, to match strings that contain only digits:
'$ ? (@ like_regex "^\\d+$")'
    Table 9.48 shows the operators and
    methods available in jsonpath.  Table 9.49 shows the available filter
    expression elements.
   
Table 9.48. jsonpath Operators and Methods
| Operator/Method | Description | Example JSON | Example Query | Result | 
|---|---|---|---|---|
| +(unary) | Plus operator that iterates over the SQL/JSON sequence | {"x": [2.85, -14.7, -9.4]} | + $.x.floor() | 2, -15, -10 | 
| -(unary) | Minus operator that iterates over the SQL/JSON sequence | {"x": [2.85, -14.7, -9.4]} | - $.x.floor() | -2, 15, 10 | 
| +(binary) | Addition | [2] | 2 + $[0] | 4 | 
| -(binary) | Subtraction | [2] | 4 - $[0] | 2 | 
| * | Multiplication | [4] | 2 * $[0] | 8 | 
| / | Division | [8] | $[0] / 2 | 4 | 
| % | Modulus | [32] | $[0] % 10 | 2 | 
| type() | Type of the SQL/JSON item | [1, "2", {}] | $[*].type() | "number", "string", "object" | 
| size() | Size of the SQL/JSON item | {"m": [11, 15]} | $.m.size() | 2 | 
| double() | Approximate floating-point number converted from an SQL/JSON number or a string | {"len": "1.9"} | $.len.double() * 2 | 3.8 | 
| ceiling() | Nearest integer greater than or equal to the SQL/JSON number | {"h": 1.3} | $.h.ceiling() | 2 | 
| floor() | Nearest integer less than or equal to the SQL/JSON number | {"h": 1.3} | $.h.floor() | 1 | 
| abs() | Absolute value of the SQL/JSON number | {"z": -0.3} | $.z.abs() | 0.3 | 
| keyvalue() | Sequence of object's key-value pairs represented as array of items
          containing three fields ( "key","value", and"id")."id"is a unique identifier of the object
          key-value pair belongs to. | {"x": "20", "y": 32} | $.keyvalue() | {"key": "x", "value": "20", "id": 0}, {"key": "y", "value": 32, "id": 0} | 
Table 9.49. jsonpath Filter Expression Elements
| Value/Predicate | Description | Example JSON | Example Query | Result | 
|---|---|---|---|---|
| == | Equality operator | [1, 2, 1, 3] | $[*] ? (@ == 1) | 1, 1 | 
| != | Non-equality operator | [1, 2, 1, 3] | $[*] ? (@ != 1) | 2, 3 | 
| <> | Non-equality operator (same as !=) | [1, 2, 1, 3] | $[*] ? (@ <> 1) | 2, 3 | 
| < | Less-than operator | [1, 2, 3] | $[*] ? (@ < 2) | 1 | 
| <= | Less-than-or-equal-to operator | [1, 2, 3] | $[*] ? (@ <= 2) | 1, 2 | 
| > | Greater-than operator | [1, 2, 3] | $[*] ? (@ > 2) | 3 | 
| >= | Greater-than-or-equal-to operator | [1, 2, 3] | $[*] ? (@ >= 2) | 2, 3 | 
| true | Value used to perform comparison with JSON trueliteral | [{"name": "John", "parent": false},
                           {"name": "Chris", "parent": true}] | $[*] ? (@.parent == true) | {"name": "Chris", "parent": true} | 
| false | Value used to perform comparison with JSON falseliteral | [{"name": "John", "parent": false},
                           {"name": "Chris", "parent": true}] | $[*] ? (@.parent == false) | {"name": "John", "parent": false} | 
| null | Value used to perform comparison with JSON nullvalue | [{"name": "Mary", "job": null},
                         {"name": "Michael", "job": "driver"}] | $[*] ? (@.job == null) .name | "Mary" | 
| && | Boolean AND | [1, 3, 7] | $[*] ? (@ > 1 && @ < 5) | 3 | 
| || | Boolean OR | [1, 3, 7] | $[*] ? (@ < 1 || @ > 5) | 7 | 
| ! | Boolean NOT | [1, 3, 7] | $[*] ? (!(@ < 5)) | 7 | 
| like_regex | Tests whether the first operand matches the regular expression
          given by the second operand, optionally with modifications
          described by a string of flagcharacters (see
          Section 9.15.2.2) | ["abc", "abd", "aBdC", "abdacb", "babc"] | $[*] ? (@ like_regex "^ab.*c" flag "i") | "abc", "aBdC", "abdacb" | 
| starts with | Tests whether the second operand is an initial substring of the first operand | ["John Smith", "Mary Stone", "Bob Johnson"] | $[*] ? (@ starts with "John") | "John Smith" | 
| exists | Tests whether a path expression matches at least one SQL/JSON item | {"x": [1, 2], "y": [2, 4]} | strict $.* ? (exists (@ ? (@[*] > 2))) | 2, 4 | 
| is unknown | Tests whether a Boolean condition is unknown | [-1, 2, 7, "infinity"] | $[*] ? ((@ > 0) is unknown) | "infinity" |