Skip to main content

Documentation Index

Fetch the complete documentation index at: https://private-7c7dfe99-page-updates.mintlify.app/llms.txt

Use this file to discover all available pages before exploring further.

​
Types of JSON functions

There are two sets of functions to parse JSON:

​
simpleJSON (visitParam) functions

ClickHouse has special functions for working with simplified JSON. All these JSON functions are based on strong assumptions about what the JSON can be. They try to do as little as possible to get the job done as quickly as possible. The following assumptions are made:
  1. The field name (function argument) must be a constant.
  2. The field name is somehow canonically encoded in JSON. For example: simpleJSONHas('{"abc":"def"}', 'abc') = 1, but simpleJSONHas('{"\\u0061\\u0062\\u0063":"def"}', 'abc') = 0
  3. Fields are searched for on any nesting level, indiscriminately. If there are multiple matching fields, the first occurrence is used.
  4. The JSON does not have space characters outside of string literals.

​
JSONExtract functions

These functions are based on simdjson, and designed for more complex JSON parsing requirements.

​
Case-Insensitive JSONExtract Functions

These functions perform ASCII case-insensitive key matching when extracting values from JSON objects. They work identically to their case-sensitive counterparts, except that object keys are matched without regard to case. When multiple keys match with different cases, the first match is returned.
These functions may be less performant than their case-sensitive counterparts, so use the regular JSONExtract functions if possible.

​
JSONAllPaths

Introduced in: v24.8.0 Returns the list of all paths stored in each row in JSON column. Syntax 
JSONAllPaths(json)
Arguments
  • json — JSON column. JSON
Returned value Returns an array of all paths in the JSON column. Array(String) Examples Usage example
Query
CREATE TABLE test (json JSON(max_dynamic_paths=1)) ENGINE = Memory;
INSERT INTO test FORMAT JSONEachRow {"json" : {"a" : 42}}, {"json" : {"b" : "Hello"}}, {"json" : {"a" : [1, 2, 3], "c" : "2020-01-01"}}
SELECT json, JSONAllPaths(json) FROM test;
Response
┌─json─────────────────────────────────┬─JSONAllPaths(json)─┐
│ {"a":"42"}                           │ ['a']              │
│ {"b":"Hello"}                        │ ['b']              │
│ {"a":["1","2","3"],"c":"2020-01-01"} │ ['a','c']          │
└──────────────────────────────────────┴────────────────────┘

​
JSONAllPathsWithTypes

Introduced in: v24.8.0 Returns the list of all paths and their data types stored in each row in JSON column. Syntax 
JSONAllPathsWithTypes(json)
Arguments
  • json — JSON column. JSON
Returned value Returns a map of all paths and their data types in the JSON column. Map(String, String) Examples Usage example
Query
CREATE TABLE test (json JSON(max_dynamic_paths=1)) ENGINE = Memory;
INSERT INTO test FORMAT JSONEachRow {"json" : {"a" : 42}}, {"json" : {"b" : "Hello"}}, {"json" : {"a" : [1, 2, 3], "c" : "2020-01-01"}}
SELECT json, JSONAllPathsWithTypes(json) FROM test;
Response
┌─json─────────────────────────────────┬─JSONAllPathsWithTypes(json)───────────────┐
│ {"a":"42"}                           │ {'a':'Int64'}                             │
│ {"b":"Hello"}                        │ {'b':'String'}                            │
│ {"a":["1","2","3"],"c":"2020-01-01"} │ {'a':'Array(Nullable(Int64))','c':'Date'} │
└──────────────────────────────────────┴───────────────────────────────────────────┘

​
JSONAllValues

Introduced in: v26.4.0 Returns all values from each row in a JSON column as an array of strings. Values are serialized in their text representation and ordered by their path names. Syntax 
JSONAllValues(json)
Arguments
  • json — JSON column. JSON
Returned value Returns an array of all values as strings in the JSON column. Array(String) Examples Usage example
Query
CREATE TABLE test (json JSON(max_dynamic_paths=1)) ENGINE = Memory;
INSERT INTO test FORMAT JSONEachRow {"json": {"a": 42}}, {"json": {"b": "Hello"}}, {"json": {"a": [1, 2, 3], "c": "2020-01-01"}}
SELECT json, JSONAllValues(json) FROM test;
Response
┌─json─────────────────────────────────┬─JSONAllValues(json)──────┐
│ {"a":42}                             │ ['42']                   │
│ {"b":"Hello"}                        │ ['Hello']                │
│ {"a":[1,2,3],"c":"2020-01-01"}       │ ['[1,2,3]','2020-01-01'] │
└──────────────────────────────────────┴──────────────────────────┘

​
JSONArrayLength

Introduced in: v23.2.0 Returns the number of elements in the outermost JSON array. The function returns NULL if input JSON string is invalid. Syntax 
JSONArrayLength(json)
Aliases: JSON_ARRAY_LENGTH Arguments
  • json — String with valid JSON. String
Returned value Returns the number of array elements if json is a valid JSON array string, otherwise returns NULL. Nullable(UInt64) Examples Usage example
Query
SELECT
    JSONArrayLength(''),
    JSONArrayLength('[1,2,3]');
Response
┌─JSONArrayLength('')─┬─JSONArrayLength('[1,2,3]')─┐
│                ᴺᵁᴸᴸ │                          3 │
└─────────────────────┴────────────────────────────┘

​
JSONDynamicPaths

Introduced in: v24.8.0 Returns the list of dynamic paths that are stored as separate subcolumns in JSON column. Syntax 
JSONDynamicPaths(json)
Arguments
  • json — JSON column. JSON
Returned value Returns an array of dynamic paths in the JSON column. Array(String) Examples Usage example
Query
CREATE TABLE test (json JSON(max_dynamic_paths=1)) ENGINE = Memory;
INSERT INTO test FORMAT JSONEachRow {"json" : {"a" : 42}}, {"json" : {"b" : "Hello"}}, {"json" : {"a" : [1, 2, 3], "c" : "2020-01-01"}}
SELECT json, JSONDynamicPaths(json) FROM test;
Response
┌─json─────────────────────────────────┬─JSONDynamicPaths(json)─┐
│ {"a":"42"}                           │ ['a']                  │
│ {"b":"Hello"}                        │ []                     │
│ {"a":["1","2","3"],"c":"2020-01-01"} │ ['a']                  │
└──────────────────────────────────────┴────────────────────────┘

​
JSONDynamicPathsWithTypes

Introduced in: v24.8.0 Returns the list of dynamic paths that are stored as separate subcolumns and their types in each row in JSON column. Syntax 
JSONDynamicPathsWithTypes(json)
Arguments
  • json — JSON column. JSON
Returned value Returns a map of dynamic paths and their data types in the JSON column. Map(String, String) Examples Usage example
Query
CREATE TABLE test (json JSON(max_dynamic_paths=1)) ENGINE = Memory;
INSERT INTO test FORMAT JSONEachRow {"json" : {"a" : 42}}, {"json" : {"b" : "Hello"}}, {"json" : {"a" : [1, 2, 3], "c" : "2020-01-01"}}
SELECT json, JSONDynamicPathsWithTypes(json) FROM test;
Response
┌─json─────────────────────────────────┬─JSONDynamicPathsWithTypes(json)─┐
│ {"a":"42"}                           │ {'a':'Int64'}                   │
│ {"b":"Hello"}                        │ {}                              │
│ {"a":["1","2","3"],"c":"2020-01-01"} │ {'a':'Array(Nullable(Int64))'}  │
└──────────────────────────────────────┴─────────────────────────────────┘

​
JSONExtract

Introduced in: v19.14.0 Parses JSON and extracts a value with given ClickHouse data type. Syntax 
JSONExtract(json[, indices_or_keys, ...], return_type)
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
  • return_type — ClickHouse data type to return. String
Returned value Returns a value of specified ClickHouse data type if possible, otherwise returns the default value for that type. Examples Usage example
Query
SELECT JSONExtract('{"a": "hello", "b": [-100, 200.0, 300]}', 'Tuple(String, Array(Float64))') AS res;
Response
┌─res──────────────────────────────┐
│ ('hello',[-100,200,300])         │
└──────────────────────────────────┘

​
JSONExtractArrayRaw

Introduced in: v20.1.0 Returns an array with elements of JSON array, each represented as unparsed string. Syntax 
JSONExtractArrayRaw(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
Returned value Returns an array of strings with JSON array elements. If the part is not an array or does not exist, an empty array will be returned. Array(String) Examples Usage example
Query
SELECT JSONExtractArrayRaw('{"a": "hello", "b": [-100, 200.0, "hello"]}', 'b') AS res;
Response
┌─res──────────────────────────┐
│ ['-100','200.0','"hello"']   │
└──────────────────────────────┘

​
JSONExtractArrayRawCaseInsensitive

Introduced in: v25.8.0 Returns an array with elements of JSON array, each represented as unparsed string, using case-insensitive key matching. This function is similar to JSONExtractArrayRaw. Syntax 
JSONExtractArrayRawCaseInsensitive(json [, indices_or_keys]...)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the array. Keys use case-insensitive matching String or (U)Int*
Returned value Returns an array of raw JSON strings. Array(String) Examples basic
Query
SELECT JSONExtractArrayRawCaseInsensitive('{"Items": [1, 2, 3]}', 'ITEMS')
Response
['1','2','3']

​
JSONExtractBool

Introduced in: v20.1.0 Parses JSON and extracts a value of Bool type. Syntax 
JSONExtractBool(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
Returned value Returns a Bool value if it exists, otherwise returns 0. Bool Examples Usage example
Query
SELECT JSONExtractBool('{"passed": true}', 'passed') AS res;
Response
┌─res─┐
│   1 │
└─────┘

​
JSONExtractBoolCaseInsensitive

Introduced in: v25.8.0 Parses JSON and extracts a boolean value using case-insensitive key matching. This function is similar to JSONExtractBool. Syntax 
JSONExtractBoolCaseInsensitive(json [, indices_or_keys]...)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the field. Keys use case-insensitive matching String or (U)Int*
Returned value Returns the extracted boolean value (1 for true, 0 for false), 0 if not found. UInt8 Examples basic
Query
SELECT JSONExtractBoolCaseInsensitive('{"IsActive": true}', 'isactive')
Response
1

​
JSONExtractCaseInsensitive

Introduced in: v25.8.0 Parses JSON and extracts a value of the given ClickHouse data type using case-insensitive key matching. This function is similar to JSONExtract. Syntax 
JSONExtractCaseInsensitive(json [, indices_or_keys...], return_type)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the field. Keys use case-insensitive matching String or (U)Int*
  • return_type — The ClickHouse data type to extract String
Returned value Returns the extracted value in the specified data type. Any Examples int_type
Query
SELECT JSONExtractCaseInsensitive('{"Number": 123}', 'number', 'Int32')
Response
123
array_type
Query
SELECT JSONExtractCaseInsensitive('{"List": [1, 2, 3]}', 'list', 'Array(Int32)')
Response
[1,2,3]

​
JSONExtractFloat

Introduced in: v20.1.0 Parses JSON and extracts a value of Float type. Syntax 
JSONExtractFloat(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
Returned value Returns a Float value if it exists, otherwise returns 0. Float64 Examples Usage example
Query
SELECT JSONExtractFloat('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', 2) AS res;
Response
┌─res─┐
│ 200 │
└─────┘

​
JSONExtractFloatCaseInsensitive

Introduced in: v25.8.0 Parses JSON and extracts a value of Float type using case-insensitive key matching. This function is similar to JSONExtractFloat. Syntax 
JSONExtractFloatCaseInsensitive(json [, indices_or_keys]...)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the field. Keys use case-insensitive matching String or (U)Int*
Returned value Returns the extracted Float value, 0 if not found or cannot be converted. Float64 Examples basic
Query
SELECT JSONExtractFloatCaseInsensitive('{"Price": 12.34}', 'PRICE')
Response
12.34

​
JSONExtractInt

Introduced in: v20.1.0 Parses JSON and extracts a value of Int type. Syntax 
JSONExtractInt(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
Returned value Returns an Int value if it exists, otherwise returns 0. Int64 Examples Usage example
Query
SELECT JSONExtractInt('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', 1) AS res;
Response
┌──res─┐
│ -100 │
└──────┘

​
JSONExtractIntCaseInsensitive

Introduced in: v25.8.0 Parses JSON and extracts a value of Int type using case-insensitive key matching. This function is similar to JSONExtractInt. Syntax 
JSONExtractIntCaseInsensitive(json [, indices_or_keys]...)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the field. Keys use case-insensitive matching String or (U)Int*
Returned value Returns the extracted Int value, 0 if not found or cannot be converted. Int64 Examples basic
Query
SELECT JSONExtractIntCaseInsensitive('{"Value": 123}', 'value')
Response
123
nested
Query
SELECT JSONExtractIntCaseInsensitive('{"DATA": {"COUNT": 42}}', 'data', 'Count')
Response
42

​
JSONExtractKeys

Introduced in: v21.11.0 Parses a JSON string and extracts the keys. Syntax 
JSONExtractKeys(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
Returned value Returns an array with the keys of the JSON object. Array(String) Examples Usage example
Query
SELECT JSONExtractKeys('{"a": "hello", "b": [-100, 200.0, 300]}') AS res;
Response
┌─res─────────┐
│ ['a','b']   │
└─────────────┘

​
JSONExtractKeysAndValues

Introduced in: v20.1.0 Parses key-value pairs from a JSON where the values are of the given ClickHouse data type. Syntax 
JSONExtractKeysAndValues(json[, indices_or_keys, ...], value_type)
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
  • value_type — ClickHouse data type of the values. String
Returned value Returns an array of tuples with the parsed key-value pairs. Array(Tuple(String, value_type)) Examples Usage example
Query
SELECT JSONExtractKeysAndValues('{"x": {"a": 5, "b": 7, "c": 11}}', 'Int8', 'x') AS res;
Response
┌─res────────────────────┐
│ [('a',5),('b',7),('c',11)] │
└────────────────────────┘

​
JSONExtractKeysAndValuesCaseInsensitive

Introduced in: v25.8.0 Parses key-value pairs from JSON using case-insensitive key matching. This function is similar to JSONExtractKeysAndValues. Syntax 
JSONExtractKeysAndValuesCaseInsensitive(json [, indices_or_keys...], value_type)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the object. Keys use case-insensitive matching String or (U)Int*
  • value_type — The ClickHouse data type of the values String
Returned value Returns an array of tuples containing key-value pairs. Array(Tuple(String, T)) Examples basic
Query
SELECT JSONExtractKeysAndValuesCaseInsensitive('{"Name": "Alice", "AGE": 30}', 'String')
Response
[('Name','Alice'),('AGE','30')]

​
JSONExtractKeysAndValuesRaw

Introduced in: v20.4.0 Returns an array of tuples with keys and values from a JSON object. All values are represented as unparsed strings. Syntax 
JSONExtractKeysAndValuesRaw(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
Returned value Returns an array of tuples with parsed key-value pairs where values are unparsed strings. Array(Tuple(String, String)) Examples Usage example
Query
SELECT JSONExtractKeysAndValuesRaw('{"a": [-100, 200.0], "b": "hello"}') AS res;
Response
┌─res──────────────────────────────────┐
│ [('a','[-100,200.0]'),('b','"hello"')] │
└──────────────────────────────────────┘

​
JSONExtractKeysAndValuesRawCaseInsensitive

Introduced in: v25.8.0 Extracts raw key-value pairs from JSON using case-insensitive key matching. This function is similar to JSONExtractKeysAndValuesRaw. Syntax 
JSONExtractKeysAndValuesRawCaseInsensitive(json [, indices_or_keys]...)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the object. Keys use case-insensitive matching String or (U)Int*
Returned value Returns an array of tuples containing key-value pairs as raw strings. Array(Tuple(String, String)) Examples basic
Query
SELECT JSONExtractKeysAndValuesRawCaseInsensitive('{"Name": "Alice", "AGE": 30}')
Response
[('Name','"Alice"'),('AGE','30')]

​
JSONExtractKeysCaseInsensitive

Introduced in: v25.8.0 Parses a JSON string and extracts the keys using case-insensitive key matching to navigate to nested objects. This function is similar to JSONExtractKeys. Syntax 
JSONExtractKeysCaseInsensitive(json [, indices_or_keys]...)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the object. Keys use case-insensitive matching String or (U)Int*
Returned value Returns an array of keys from the JSON object. Array(String) Examples basic
Query
SELECT JSONExtractKeysCaseInsensitive('{"Name": "Alice", "AGE": 30}')
Response
['Name','AGE']
nested
Query
SELECT JSONExtractKeysCaseInsensitive('{"User": {"name": "John", "AGE": 25}}', 'user')
Response
['name','AGE']

​
JSONExtractRaw

Introduced in: v20.1.0 Returns a part of JSON as unparsed string. Syntax 
JSONExtractRaw(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
Returned value Returns the part of JSON as an unparsed string. If the part does not exist or has a wrong type, an empty string will be returned. String Examples Usage example
Query
SELECT JSONExtractRaw('{"a": "hello", "b": [-100, 200.0, 300]}', 'b') AS res;
Response
┌─res──────────────┐
│ [-100,200.0,300] │
└──────────────────┘

​
JSONExtractRawCaseInsensitive

Introduced in: v25.8.0 Returns part of the JSON as an unparsed string using case-insensitive key matching. This function is similar to JSONExtractRaw. Syntax 
JSONExtractRawCaseInsensitive(json [, indices_or_keys]...)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the field. Keys use case-insensitive matching String or (U)Int*
Returned value Returns the raw JSON string of the extracted element. String Examples object
Query
SELECT JSONExtractRawCaseInsensitive('{"Object": {"key": "value"}}', 'OBJECT')
Response
{"key":"value"}

​
JSONExtractString

Introduced in: v20.1.0 Parses JSON and extracts a value of String type. Syntax 
JSONExtractString(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
Returned value Returns a String value if it exists, otherwise returns an empty string. String Examples Usage example
Query
SELECT JSONExtractString('{"a": "hello", "b": [-100, 200.0, 300]}', 'a') AS res;
Response
┌─res───┐
│ hello │
└───────┘

​
JSONExtractStringCaseInsensitive

Introduced in: v25.8.0 Parses JSON and extracts a string using case-insensitive key matching. This function is similar to JSONExtractString. Syntax 
JSONExtractStringCaseInsensitive(json [, indices_or_keys]...)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the field. Keys use case-insensitive matching String or (U)Int*
Returned value Returns the extracted string value, empty string if not found. String Examples basic
Query
SELECT JSONExtractStringCaseInsensitive('{"ABC": "def"}', 'abc')
Response
def
nested
Query
SELECT JSONExtractStringCaseInsensitive('{"User": {"Name": "John"}}', 'user', 'name')
Response
John

​
JSONExtractUInt

Introduced in: v20.1.0 Parses JSON and extracts a value of UInt type. Syntax 
JSONExtractUInt(json [, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — A list of zero or more arguments each of which can be either string or integer. String or (U)Int*
Returned value Returns a UInt value if it exists, otherwise returns 0. UInt64 Examples Usage example
Query
SELECT JSONExtractUInt('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', -1) AS res;
Response
┌─res─┐
│ 300 │
└─────┘

​
JSONExtractUIntCaseInsensitive

Introduced in: v25.8.0 Parses JSON and extracts a value of UInt type using case-insensitive key matching. This function is similar to JSONExtractUInt. Syntax 
JSONExtractUIntCaseInsensitive(json [, indices_or_keys]...)
Arguments
  • json — JSON string to parse String
  • indices_or_keys — Optional. Indices or keys to navigate to the field. Keys use case-insensitive matching String or (U)Int*
Returned value Returns the extracted UInt value, 0 if not found or cannot be converted. UInt64 Examples basic
Query
SELECT JSONExtractUIntCaseInsensitive('{"COUNT": 789}', 'count')
Response
789

​
JSONHas

Introduced in: v20.1.0 Checks for the existence of the provided value(s) in the JSON document. Syntax 
JSONHas(json[ ,indices_or_keys, ...])
Arguments
  • json — JSON string to parse String
  • [ ,indices_or_keys, ...] — A list of zero or more arguments. String or (U)Int*
Returned value Returns 1 if the value exists in json, otherwise 0 UInt8 Examples Usage example
Query
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 'b') = 1;
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', 4) = 0;
Response
1
0

​
JSONKey

Introduced in: v20.1.0 Returns the key of a JSON object field by its index (1-based). If the JSON is passed as a string, it is parsed first. The second argument is a JSON path to navigate into nested objects. The function returns the key name at the specified position. Syntax 
JSONKey(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse. String
  • indices_or_keys — Optional list of indices or keys specifying a path to a nested element. Each argument can be either a string (access by key) or an integer (access by index starting from 1). String or Int*
Returned value Returns the key name at the specified position in the JSON object. String Examples Usage example
Query
SELECT JSONKey('{"a": "hello", "b": [-100, 200.0, 300]}', 1);
Response
a

​
JSONLength

Introduced in: v20.1.0 Return the length of a JSON array or a JSON object. If the value does not exist or has the wrong type, 0 will be returned. Syntax 
JSONLength(json [, indices_or_keys, ...])
Arguments Returned value Returns the length of the JSON array or JSON object, otherwise returns 0 if the value does not exist or has the wrong type. UInt64 Examples Usage example
Query
SELECT JSONLength('{"a": "hello", "b": [-100, 200.0, 300]}', 'b') = 3;
SELECT JSONLength('{"a": "hello", "b": [-100, 200.0, 300]}') = 2;
Response
1
1

​
JSONMergePatch

Introduced in: v23.10.0 Returns the merged JSON object string which is formed by merging multiple JSON objects. Syntax 
JSONMergePatch(json1[, json2, ...])
Aliases: jsonMergePatch Arguments
  • json1[, json2, ...] — One or more strings with valid JSON. String
Returned value Returns the merged JSON object string, if the JSON object strings are valid. String Examples Usage example
Query
SELECT JSONMergePatch('{"a":1}', '{"name": "joey"}', '{"name": "tom"}', '{"name": "zoey"}') AS res;
Response
┌─res───────────────────┐
│ {"a":1,"name":"zoey"} │
└───────────────────────┘

​
JSONSharedDataPaths

Introduced in: v24.8.0 Returns the list of paths that are stored in shared data structure in JSON column. Syntax 
JSONSharedDataPaths(json)
Arguments
  • json — JSON column. JSON
Returned value Returns an array of paths stored in shared data structure in the JSON column. Array(String) Examples Usage example
Query
CREATE TABLE test (json JSON(max_dynamic_paths=1)) ENGINE = Memory;
INSERT INTO test FORMAT JSONEachRow {"json" : {"a" : 42}}, {"json" : {"b" : "Hello"}}, {"json" : {"a" : [1, 2, 3], "c" : "2020-01-01"}}
SELECT json, JSONSharedDataPaths(json) FROM test;
Response
┌─json─────────────────────────────────┬─JSONSharedDataPaths(json)─┐
│ {"a":"42"}                           │ []                        │
│ {"b":"Hello"}                        │ ['b']                     │
│ {"a":["1","2","3"],"c":"2020-01-01"} │ ['c']                     │
└──────────────────────────────────────┴───────────────────────────┘

​
JSONSharedDataPathsWithTypes

Introduced in: v24.8.0 Returns the list of paths that are stored in shared data structure and their types in each row in JSON column. Syntax 
JSONSharedDataPathsWithTypes(json)
Arguments
  • json — JSON column. JSON
Returned value Returns a map of paths stored in shared data structure and their data types in the JSON column. Map(String, String) Examples Usage example
Query
CREATE TABLE test (json JSON(max_dynamic_paths=1)) ENGINE = Memory;
INSERT INTO test FORMAT JSONEachRow {"json" : {"a" : 42}}, {"json" : {"b" : "Hello"}}, {"json" : {"a" : [1, 2, 3], "c" : "2020-01-01"}}
SELECT json, JSONSharedDataPathsWithTypes(json) FROM test;
Response
┌─json─────────────────────────────────┬─JSONSharedDataPathsWithTypes(json)─┐
│ {"a":"42"}                           │ {}                                  │
│ {"b":"Hello"}                        │ {'b':'String'}                      │
│ {"a":["1","2","3"],"c":"2020-01-01"} │ {'c':'Date'}                        │
└──────────────────────────────────────┴─────────────────────────────────────┘

​
JSONType

Introduced in: v20.1.0 Return the type of a JSON value. If the value does not exist, Null=0 will be returned. Syntax 
JSONType(json[, indices_or_keys, ...])
Arguments
  • json — JSON string to parse String
  • json[, indices_or_keys, ...] — A list of zero or more arguments, each of which can be either string or integer. String or (U)Int8/16/32/64
Returned value Returns the type of a JSON value as a string, otherwise if the value doesn’t exist it returns Null=0 Enum Examples Usage example
Query
SELECT JSONType('{"a": "hello", "b": [-100, 200.0, 300]}') = 'Object';
SELECT JSONType('{"a": "hello", "b": [-100, 200.0, 300]}', 'a') = 'String';
SELECT JSONType('{"a": "hello", "b": [-100, 200.0, 300]}', 'b') = 'Array';
Response
1
1
1

​
JSON_EXISTS

Introduced in: v21.8.0 If the value exists in the JSON document, 1 will be returned. If the value does not exist, 0 will be returned. Syntax 
JSON_EXISTS(json, path)
Arguments
  • json — A string with valid JSON. String
  • path — A string representing the path. String
Returned value Returns 1 if the value exists in the JSON document, otherwise 0. UInt8 Examples Usage example
Query
SELECT JSON_EXISTS('{"hello":1}', '$.hello');
SELECT JSON_EXISTS('{"hello":{"world":1}}', '$.hello.world');
SELECT JSON_EXISTS('{"hello":["world"]}', '$.hello[*]');
SELECT JSON_EXISTS('{"hello":["world"]}', '$.hello[0]');
Response
┌─JSON_EXISTS(⋯ '$.hello')─┐
│                        1 │
└──────────────────────────┘
┌─JSON_EXISTS(⋯llo.world')─┐
│                        1 │
└──────────────────────────┘
┌─JSON_EXISTS(⋯.hello[*]')─┐
│                        1 │
└──────────────────────────┘
┌─JSON_EXISTS(⋯.hello[0]')─┐
│                        1 │
└──────────────────────────┘

​
JSON_QUERY

Introduced in: v21.8.0 Parses a JSON and extract a value as a JSON array or JSON object. If the value does not exist, an empty string will be returned. Syntax 
JSON_QUERY(json, path)
Arguments
  • json — A string with valid JSON. String
  • path — A string representing the path. String
Returned value Returns the extracted JSON array or JSON object as a string, or an empty string if the value does not exist. String Examples Usage example
Query
SELECT JSON_QUERY('{"hello":"world"}', '$.hello');
SELECT JSON_QUERY('{"array":[[0, 1, 2, 3, 4, 5], [0, -1, -2, -3, -4, -5]]}', '$.array[*][0 to 2, 4]');
SELECT JSON_QUERY('{"hello":2}', '$.hello');
SELECT toTypeName(JSON_QUERY('{"hello":2}', '$.hello'));
Response
["world"]
[0, 1, 4, 0, -1, -4]
[2]
String

​
JSON_VALUE

Introduced in: v21.11.0 Parses a JSON and extract a value as a JSON scalar. If the value does not exist, an empty string will be returned by default. This function is controlled by the following settings:
  • by SET function_json_value_return_type_allow_nullable = true, NULL will be returned. If the value is complex type (such as: struct, array, map), an empty string will be returned by default.
  • by SET function_json_value_return_type_allow_complex = true, the complex value will be returned.
Syntax 
JSON_VALUE(json, path)
Arguments
  • json — A string with valid JSON. String
  • path — A string representing the path. String
Returned value Returns the extracted JSON scalar as a string, or an empty string if the value does not exist. String Examples Usage example
Query
SELECT JSON_VALUE('{"hello":"world"}', '$.hello');
SELECT JSON_VALUE('{"array":[[0, 1, 2, 3, 4, 5], [0, -1, -2, -3, -4, -5]]}', '$.array[*][0 to 2, 4]');
SELECT JSON_VALUE('{"hello":2}', '$.hello');
SELECT JSON_VALUE('{"hello":"world"}', '$.b') settings function_json_value_return_type_allow_nullable=true;
Response
world
0
2
ᴺᵁᴸᴸ

​
dynamicElement

Introduced in: v24.1.0 Extracts a column with specified type from a Dynamic column. This function allows you to extract values of a specific type from a Dynamic column. If a row contains a value of the requested type, it returns that value. If the row contains a different type or NULL, it returns NULL for scalar types or an empty array for array types. Syntax 
dynamicElement(dynamic, type_name)
Arguments
  • dynamic — Dynamic column to extract from. Dynamic
  • type_name — The name of the variant type to extract (e.g., ‘String’, ‘Int64’, ‘Array(Int64)’).
Returned value Returns values of the specified type from the Dynamic column. Returns NULL for non-matching types (or empty array for array types). Any Examples Extracting different types from Dynamic column
Query
CREATE TABLE test (d Dynamic) ENGINE = Memory;
INSERT INTO test VALUES (NULL), (42), ('Hello, World!'), ([1, 2, 3]);
SELECT d, dynamicType(d), dynamicElement(d, 'String'), dynamicElement(d, 'Int64'), dynamicElement(d, 'Array(Int64)'), dynamicElement(d, 'Date'), dynamicElement(d, 'Array(String)') FROM test
Response
┌─d─────────────┬─dynamicType(d)─┬─dynamicElement(d, 'String')─┬─dynamicElement(d, 'Int64')─┬─dynamicElement(d, 'Array(Int64)')─┬─dynamicElement(d, 'Date')─┬─dynamicElement(d, 'Array(String)')─┐
│ ᴺᵁᴸᴸ          │ None           │ ᴺᵁᴸᴸ                        │                       ᴺᵁᴸᴸ │ []                                │                      ᴺᵁᴸᴸ │ []                                 │
│ 42            │ Int64          │ ᴺᵁᴸᴸ                        │                         42 │ []                                │                      ᴺᵁᴸᴸ │ []                                 │
│ Hello, World! │ String         │ Hello, World!               │                       ᴺᵁᴸᴸ │ []                                │                      ᴺᵁᴸᴸ │ []                                 │
│ [1,2,3]       │ Array(Int64)   │ ᴺᵁᴸᴸ                        │                       ᴺᵁᴸᴸ │ [1,2,3]                           │                      ᴺᵁᴸᴸ │ []                                 │
└───────────────┴────────────────┴─────────────────────────────┴────────────────────────────┴───────────────────────────────────┴───────────────────────────┴────────────────────────────────────┘

​
dynamicType

Introduced in: v24.1.0 Returns the variant type name for each row of a Dynamic column. For rows containing NULL, the function returns ‘None’. For all other rows, it returns the actual data type stored in that row of the Dynamic column (e.g., ‘Int64’, ‘String’, ‘Array(Int64)’). Syntax 
dynamicType(dynamic)
Arguments
  • dynamic — Dynamic column to inspect. Dynamic
Returned value Returns the type name of the value stored in each row, or ‘None’ for NULL values. String Examples Inspecting types in Dynamic column
Query
CREATE TABLE test (d Dynamic) ENGINE = Memory;
INSERT INTO test VALUES (NULL), (42), ('Hello, World!'), ([1, 2, 3]);
SELECT d, dynamicType(d) FROM test;
Response
┌─d─────────────┬─dynamicType(d)─┐
│ ᴺᵁᴸᴸ          │ None           │
│ 42            │ Int64          │
│ Hello, World! │ String         │
│ [1,2,3]       │ Array(Int64)   │
└───────────────┴────────────────┘

​
isDynamicElementInSharedData

Introduced in: v24.1.0 Returns true for rows in a Dynamic column that are stored in shared variant format rather than as separate subcolumns. When a Dynamic column has a max_types limit, values that exceed this limit are stored in a shared binary format instead of being separated into individual typed subcolumns. This function identifies which rows are stored in this shared format. Syntax 
isDynamicElementInSharedData(dynamic)
Arguments
  • dynamic — Dynamic column to inspect. Dynamic
Returned value Returns true if the value is stored in shared variant format, false if stored as a separate subcolumn or is NULL. Bool Examples Checking storage format in Dynamic column with max_types limit
Query
CREATE TABLE test (d Dynamic(max_types=2)) ENGINE = Memory;
INSERT INTO test VALUES (NULL), (42), ('Hello, World!'), ([1, 2, 3]);
SELECT d, isDynamicElementInSharedData(d) FROM test;
Response
┌─d─────────────┬─isDynamicElementInSharedData(d)─┐
│ ᴺᵁᴸᴸ          │ false                           │
│ 42            │ false                           │
│ Hello, World! │ true                            │
│ [1,2,3]       │ true                            │
└───────────────┴─────────────────────────────────┘

​
isValidJSON

Introduced in: v20.1.0 Checks that the string passed is valid JSON. Syntax 
isValidJSON(json)
Arguments
  • json — JSON string to validate String
Returned value Returns 1 if the string is valid JSON, otherwise 0. UInt8 Examples Usage example
Query
SELECT isValidJSON('{"a": "hello", "b": [-100, 200.0, 300]}') = 1;
SELECT isValidJSON('not JSON') = 0;
Response
1
0
Using integers to access both JSON arrays and JSON objects
Query
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 0);
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 1);
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 2);
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', -1);
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', -2);
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 3);
Response
0
1
1
1
1
1
0

​
simpleJSONExtractBool

Introduced in: v21.4.0 Parses a true/false value from the value of the field named field_name. The result is UInt8. Syntax 
simpleJSONExtractBool(json, field_name)
Aliases: visitParamExtractBool Arguments
  • json — The JSON in which the field is searched for. String
  • field_name — The name of the field to search for. const String
Returned value Returns 1 if the value of the field is true, 0 otherwise. This means this function will return 0 including (and not only) in the following cases:
  • If the field doesn’t exists.
  • If the field contains true as a string, e.g.: {"field":"true"}.
  • If the field contains 1 as a numerical value. UInt8
Examples Usage example
Query
CREATE TABLE jsons
(
    `json` String
)
ENGINE = MergeTree
ORDER BY tuple();

INSERT INTO jsons VALUES ('{"foo":false,"bar":true}');
INSERT INTO jsons VALUES ('{"foo":"true","qux":1}');

SELECT simpleJSONExtractBool(json, 'bar') FROM jsons ORDER BY json;
SELECT simpleJSONExtractBool(json, 'foo') FROM jsons ORDER BY json;
Response
0
1
0
0

​
simpleJSONExtractFloat

Introduced in: v21.4.0 Parses Float64 from the value of the field named field_name. If field_name is a string field, it tries to parse a number from the beginning of the string. If the field does not exist, or it exists but does not contain a number, it returns 0. Syntax 
simpleJSONExtractFloat(json, field_name)
Aliases: visitParamExtractFloat Arguments
  • json — The JSON in which the field is searched for. String
  • field_name — The name of the field to search for. const String
Returned value Returns the number parsed from the field if the field exists and contains a number, otherwise 0. Float64 Examples Usage example
Query
CREATE TABLE jsons
(
    `json` String
)
ENGINE = MergeTree
ORDER BY tuple();

INSERT INTO jsons VALUES ('{"foo":"-4e3"}');
INSERT INTO jsons VALUES ('{"foo":-3.4}');
INSERT INTO jsons VALUES ('{"foo":5}');
INSERT INTO jsons VALUES ('{"foo":"not1number"}');
INSERT INTO jsons VALUES ('{"baz":2}');

SELECT simpleJSONExtractFloat(json, 'foo') FROM jsons ORDER BY json;
Response
0
-4000
0
-3.4
5

​
simpleJSONExtractInt

Introduced in: v21.4.0 Parses Int64 from the value of the field named field_name. If field_name is a string field, it tries to parse a number from the beginning of the string. If the field does not exist, or it exists but does not contain a number, it returns 0. Syntax 
simpleJSONExtractInt(json, field_name)
Aliases: visitParamExtractInt Arguments
  • json — The JSON in which the field is searched for. String
  • field_name — The name of the field to search for. const String
Returned value Returns the number parsed from the field if the field exists and contains a number, 0 otherwise Int64 Examples Usage example
Query
CREATE TABLE jsons
(
    `json` String
)
ENGINE = MergeTree
ORDER BY tuple();

INSERT INTO jsons VALUES ('{"foo":"-4e3"}');
INSERT INTO jsons VALUES ('{"foo":-3.4}');
INSERT INTO jsons VALUES ('{"foo":5}');
INSERT INTO jsons VALUES ('{"foo":"not1number"}');
INSERT INTO jsons VALUES ('{"baz":2}');

SELECT simpleJSONExtractInt(json, 'foo') FROM jsons ORDER BY json;
Response
0
-4
0
-3
5

​
simpleJSONExtractRaw

Introduced in: v21.4.0 Returns the value of the field named field_name as a String, including separators. Syntax 
simpleJSONExtractRaw(json, field_name)
Aliases: visitParamExtractRaw Arguments
  • json — The JSON in which the field is searched for. String
  • field_name — The name of the field to search for. const String
Returned value Returns the value of the field as a string, including separators if the field exists, or an empty string otherwise String Examples Usage example
Query
CREATE TABLE jsons
(
    `json` String
)
ENGINE = MergeTree
ORDER BY tuple();

INSERT INTO jsons VALUES ('{"foo":"-4e3"}');
INSERT INTO jsons VALUES ('{"foo":-3.4}');
INSERT INTO jsons VALUES ('{"foo":5}');
INSERT INTO jsons VALUES ('{"foo":{"def":[1,2,3]}}');
INSERT INTO jsons VALUES ('{"baz":2}');

SELECT simpleJSONExtractRaw(json, 'foo') FROM jsons ORDER BY json;
Response
"-4e3"
-3.4
5
{"def":[1,2,3]}

​
simpleJSONExtractString

Introduced in: v21.4.0 Parses String in double quotes from the value of the field named field_name. Implementation details There is currently no support for code points in the format \uXXXX\uYYYY that are not from the basic multilingual plane (they are converted to CESU-8 instead of UTF-8). Syntax 
simpleJSONExtractString(json, field_name)
Aliases: visitParamExtractString Arguments
  • json — The JSON in which the field is searched for. String
  • field_name — The name of the field to search for. const String
Returned value Returns the unescaped value of a field as a string, including separators. An empty string is returned if the field doesn’t contain a double quoted string, if unescaping fails or if the field doesn’t exist String Examples Usage example
Query
CREATE TABLE jsons
(
    `json` String
)
ENGINE = MergeTree
ORDER BY tuple();

INSERT INTO jsons VALUES ('{"foo":"\\n\\u0000"}');
INSERT INTO jsons VALUES ('{"foo":"\\u263"}');
INSERT INTO jsons VALUES ('{"foo":"\\u263a"}');
INSERT INTO jsons VALUES ('{"foo":"hello}');

SELECT simpleJSONExtractString(json, 'foo') FROM jsons ORDER BY json;
Response
\n\0

☺

​
simpleJSONExtractUInt

Introduced in: v21.4.0 Parses UInt64 from the value of the field named field_name. If field_name is a string field, it tries to parse a number from the beginning of the string. If the field does not exist, or it exists but does not contain a number, it returns 0. Syntax 
simpleJSONExtractUInt(json, field_name)
Aliases: visitParamExtractUInt Arguments
  • json — The JSON in which the field is searched for. String
  • field_name — The name of the field to search for. const String
Returned value Returns the number parsed from the field if the field exists and contains a number, 0 otherwise UInt64 Examples Usage example
Query
CREATE TABLE jsons
(
    `json` String
)
ENGINE = MergeTree
ORDER BY tuple();

INSERT INTO jsons VALUES ('{"foo":"4e3"}');
INSERT INTO jsons VALUES ('{"foo":3.4}');
INSERT INTO jsons VALUES ('{"foo":5}');
INSERT INTO jsons VALUES ('{"foo":"not1number"}');
INSERT INTO jsons VALUES ('{"baz":2}');

SELECT simpleJSONExtractUInt(json, 'foo') FROM jsons ORDER BY json;
Response
0
4
0
3
5

​
simpleJSONHas

Introduced in: v21.4.0 Checks whether there is a field named field_name. Syntax 
simpleJSONHas(json, field_name)
Aliases: visitParamHas Arguments
  • json — The JSON in which the field is searched for. String
  • field_name — The name of the field to search for. const String
Returned value Returns 1 if the field exists, 0 otherwise UInt8 Examples Usage example
Query
CREATE TABLE jsons
(
    `json` String
)
ENGINE = MergeTree
ORDER BY tuple();

INSERT INTO jsons VALUES ('{"foo":"true","qux":1}');

SELECT simpleJSONHas(json, 'foo') FROM jsons;
SELECT simpleJSONHas(json, 'bar') FROM jsons;
Response
1
0

​
toJSONString

Introduced in: v21.7.0 Serializes a value to its JSON representation. Various data types and nested structures are supported. 64-bit integers or bigger (like UInt64 or Int128) are enclosed in quotes by default. output_format_json_quote_64bit_integers controls this behavior. Special values NaN and inf are replaced with null. Enable output_format_json_quote_denormals setting to show them. When serializing an Enum value, the function outputs its name. See also: Syntax 
toJSONString(value)
Arguments
  • value — Value to serialize. Value may be of any data type. Any
Returned value Returns the JSON representation of the value. String Examples Map serialization
Query
SELECT toJSONString(map('key1', 1, 'key2', 2));
Response
┌─toJSONString(map('key1', 1, 'key2', 2))─┐
│ {"key1":1,"key2":2}                     │
└─────────────────────────────────────────┘
Special values
Query
SELECT toJSONString(tuple(1.25, NULL, NaN, +inf, -inf, [])) SETTINGS output_format_json_quote_denormals = 1;
Response
┌─toJSONString(tuple(1.25, NULL, NaN, plus(inf), minus(inf), []))─┐
│ [1.25,null,"nan","inf","-inf",[]]                               │
└─────────────────────────────────────────────────────────────────┘