JSON Functions

There are two sets of functions to parse JSON:

simpleJSON* ( visitParam* ) which is made for parsing a limited subset of JSON extremely fast.

JSONExtract* which is made for parsing ordinary 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:

The field name (function argument) must be a constant.

The field name is somehow canonically encoded in JSON. For example: simpleJSONHas('{"abc":"def"}', 'abc') = 1 , but simpleJSONHas('{"\\u0061\\u0062\\u0063":"def"}', 'abc') = 0

Fields are searched for on any nesting level, indiscriminately. If there are multiple matching fields, the first occurrence is used.

The JSON does not have space characters outside of string literals.

simpleJSONHas ​

Checks whether there is a field named field_name . The result is UInt8 .

Syntax

Alias: visitParamHas .

Parameters

json — The JSON in which the field is searched for. String

field_name — The name of the field to search for. String literal

Returned value

Returns 1 if the field exists, 0 otherwise. UInt8 .

Example

Query:

Result:

simpleJSONExtractUInt ​

Parses UInt64 from the value of the field named field_name . If this 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

Alias: visitParamExtractUInt .

Parameters

json — The JSON in which the field is searched for. String

field_name — The name of the field to search for. String literal

Returned value

Returns the number parsed from the field if the field exists and contains a number, 0 otherwise. UInt64 .

Example

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Result:

simpleJSONExtractInt ​

Parses Int64 from the value of the field named field_name . If this 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

Alias: visitParamExtractInt .

Parameters

json — The JSON in which the field is searched for. String

field_name — The name of the field to search for. String literal

Returned value

Returns the number parsed from the field if the field exists and contains a number, 0 otherwise. Int64 .

Example

Query:

Result:

simpleJSONExtractFloat ​

Parses Float64 from the value of the field named field_name . If this 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

Alias: visitParamExtractFloat .

Parameters

json — The JSON in which the field is searched for. String

field_name — The name of the field to search for. String literal

Returned value

Returns the number parsed from the field if the field exists and contains a number, 0 otherwise. Float64 .

Example

Query:

Result:

simpleJSONExtractBool ​

Parses a true/false value from the value of the field named field_name . The result is UInt8 .

Syntax

Alias: visitParamExtractBool .

Parameters

json — The JSON in which the field is searched for. String

field_name — The name of the field to search for. String literal

Returned value

It 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.

Example

Query:

Result:

simpleJSONExtractRaw ​

Returns the value of the field named field_name as a String , including separators.

Syntax

Alias: visitParamExtractRaw .

Parameters

json — The JSON in which the field is searched for. String

field_name — The name of the field to search for. String literal

Returned value

Returns the value of the field as a string, including separators if the field exists, or an empty string otherwise. String

Example

Query:

Result:

simpleJSONExtractString ​

Parses String in double quotes from the value of the field named field_name .

Syntax

Alias: visitParamExtractString .

Parameters

json — The JSON in which the field is searched for. String

field_name — The name of the field to search for. String literal

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 .

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).

Example

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Result:

JSONExtract functions ​

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

isValidJSON ​

Checks that passed string is valid JSON.

Syntax

Examples

JSONHas ​

If the value exists in the JSON document, 1 will be returned. If the value does not exist, 0 will be returned.

Syntax

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns 1 if the value exists in json , otherwise 0 . UInt8 .

Examples

Query:

The minimum index of the element is 1. Thus the element 0 does not exist. You may use integers to access both JSON arrays and JSON objects. For example:

JSONLength ​

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

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns the length of the JSON array or JSON object. Returns 0 if the value does not exist or has the wrong type. UInt64 .

Examples

JSONType ​

Return the type of a JSON value. If the value does not exist, Null=0 will be returned (not usual Null , but Null=0 of Enum8('Null' = 0, 'String' = 34,... ). .

Syntax

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns the type of a JSON value as a string, otherwise if the value doesn't exists it returns Null=0 . Enum .

Examples

JSONExtractUInt ​

Parses JSON and extracts a value of UInt type.

Syntax

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns a UInt value if it exists, otherwise it returns 0 . UInt64 .

Examples

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Result:

JSONExtractInt ​

Parses JSON and extracts a value of Int type.

Syntax

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns an Int value if it exists, otherwise it returns 0 . Int64 .

Examples

Query:

Result:

JSONExtractFloat ​

Parses JSON and extracts a value of Int type.

Syntax

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns an Float value if it exists, otherwise it returns 0 . Float64 .

Examples

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Result:

JSONExtractBool ​

Parses JSON and extracts a boolean value. If the value does not exist or has a wrong type, 0 will be returned.

Syntax

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns a Boolean value if it exists, otherwise it returns 0 . Bool .

Example

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JSONExtractString ​

Parses JSON and extracts a string. This function is similar to visitParamExtractString functions. If the value does not exist or has a wrong type, an empty string will be returned.

Syntax

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns an unescaped string from json . If unescaping failed, if the value does not exist or if it has a wrong type then it returns an empty string. String .

Examples

JSONExtract ​

Parses JSON and extracts a value of the given ClickHouse data type. This function is a generalized version of the previous JSONExtract<type> functions. Meaning:

JSONExtract(..., 'String') returns exactly the same as JSONExtractString() , JSONExtract(..., 'Float64') returns exactly the same as JSONExtractFloat() .

Syntax

Parameters

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 , Int* .

return_type — A string specifying the type of the value to extract. String .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns a value if it exists of the specified return type, otherwise it returns 0 , Null , or an empty-string depending on the specified return type. UInt64 , Int64 , Float64 , Bool or String .

Examples

Referring to a nested values by passing multiple indices_or_keys parameters:

Result:

JSONExtractKeysAndValues ​

Parses key-value pairs from JSON where the values are of the given ClickHouse data type.

Syntax

Parameters

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 , Int* .

value_type — A string specifying the type of the value to extract. String .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns an array of parsed key-value pairs. Array ( Tuple ( value_type )).

Example

JSONExtractKeys ​

Parses a JSON string and extracts the keys.

Syntax

Parameters

json — String with valid JSON.

a, b, c... — Comma-separated indices or keys that specify the path to the inner field in a nested JSON object. Each argument can be either a String to get the field by the key or an Integer to get the N-th field (indexed from 1, negative integers count from the end). If not set, the whole JSON is parsed as the top-level object. Optional parameter.

Returned value

Returns an array with the keys of the JSON. Array ( String ).

Example

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JSONExtractRaw ​

Returns part of the JSON as an unparsed string. If the part does not exist or has the wrong type, an empty string will be returned.

Syntax

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns part of the JSON as an unparsed string. If the part does not exist or has the wrong type, an empty string is returned. String .

Example

Case-Insensitive JSONExtract Functions ​

The following 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.

JSONExtractIntCaseInsensitive ​

Parses JSON and extracts a value of Int type using case-insensitive key matching. This function is similar to JSONExtractInt .

Syntax

Example

JSONExtractUIntCaseInsensitive ​

Parses JSON and extracts a value of UInt type using case-insensitive key matching. This function is similar to JSONExtractUInt .

Syntax

Example

JSONExtractFloatCaseInsensitive ​

Parses JSON and extracts a value of Float type using case-insensitive key matching. This function is similar to JSONExtractFloat .

Syntax

Example

JSONExtractBoolCaseInsensitive ​

Parses JSON and extracts a boolean value using case-insensitive key matching. This function is similar to JSONExtractBool .

Syntax

Example

JSONExtractStringCaseInsensitive ​

Parses JSON and extracts a string using case-insensitive key matching. This function is similar to JSONExtractString .

Syntax

Example

JSONExtractCaseInsensitive ​

Parses JSON and extracts a value of the given ClickHouse data type using case-insensitive key matching. This function is similar to JSONExtract .

Syntax

Example

JSONExtractKeysAndValuesCaseInsensitive ​

Parses key-value pairs from JSON using case-insensitive key matching. This function is similar to JSONExtractKeysAndValues .

Syntax

Example

JSONExtractRawCaseInsensitive ​

Returns part of the JSON as an unparsed string using case-insensitive key matching. This function is similar to JSONExtractRaw .

Syntax

Example

JSONExtractArrayRawCaseInsensitive ​

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

Example

JSONExtractKeysAndValuesRawCaseInsensitive ​

Extracts raw key-value pairs from JSON using case-insensitive key matching. This function is similar to JSONExtractKeysAndValuesRaw .

Syntax

Example

JSONExtractKeysCaseInsensitive ​

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

Example

JSONExtractArrayRaw ​

Returns an array with elements of JSON array, each represented as unparsed string. If the part does not exist or isn't an array, then an empty array will be returned.

Syntax

Parameters

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 , Int* .

indices_or_keys type:

String = access object member by key.

Positive integer = access the n-th member/key from the beginning.

Negative integer = access the n-th member/key from the end.

Returned value

Returns an array with elements of JSON array, each represented as unparsed string. Otherwise, an empty array is returned if the part does not exist or is not an array. Array ( String ).

Example

JSONExtractKeysAndValuesRaw ​

Extracts raw data from a JSON object.

Syntax

Arguments

json — String with valid JSON.

p, a, t, h — Comma-separated indices or keys that specify the path to the inner field in a nested JSON object. Each argument can be either a string to get the field by the key or an integer to get the N-th field (indexed from 1, negative integers count from the end). If not set, the whole JSON is parsed as the top-level object. Optional parameter.

Returned values

Array with ('key', 'value') tuples. Both tuple members are strings. Array ( Tuple ( String , String ).

Empty array if the requested object does not exist, or input JSON is invalid. Array ( Tuple ( String , String ).

Examples

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Result:

Query:

Result:

Query:

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JSON_EXISTS ​

If the value exists in the JSON document, 1 will be returned. If the value does not exist, 0 will be returned.

Syntax

Parameters

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 .

Examples

JSON_QUERY ​

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

Parameters

json — A string with valid JSON. String .

path — A string representing the path. String .

Returned value

Returns the extracted value as a JSON array or JSON object. Otherwise it returns an empty string if the value does not exist. String .

Example

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Result:

JSON_VALUE ​

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

Parameters

json — A string with valid JSON. String .

path — A string representing the path. String .

Returned value

Returns the extracted value as a JSON scalar if it exists, otherwise an empty string is returned. String .

Example

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toJSONString ​

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.

Syntax

Arguments

value — Value to serialize. Value may be of any data type.

Returned value

JSON representation of the value. String .

Example

The first example shows serialization of a Map . The second example shows some special values wrapped into a Tuple .

Query:

Result:

See Also

output_format_json_quote_64bit_integers

output_format_json_quote_denormals

JSONArrayLength ​

Returns the number of elements in the outermost JSON array. The function returns NULL if input JSON string is invalid.

Syntax

Alias: JSON_ARRAY_LENGTH(json) .

Arguments

json — String with valid JSON.

Returned value

If json is a valid JSON array string, returns the number of array elements, otherwise returns NULL. Nullable(UInt64) .

Example

jsonMergePatch ​

Returns the merged JSON object string which is formed by merging multiple JSON objects.

Syntax

Arguments

json — String with valid JSON.

Returned value

If JSON object strings are valid, return the merged JSON object string. String .

Example

JSONAllPaths ​

Returns the list of all paths stored in each row in JSON column.

Syntax

Arguments

json — JSON .

Returned value

An array of paths. Array(String) .

Example

JSONAllPathsWithTypes ​

Returns the map of all paths and their data types stored in each row in JSON column.

Syntax

Arguments

json — JSON .

Returned value

An array of paths. Map(String, String) .

Example

JSONDynamicPaths ​

Returns the list of dynamic paths that are stored as separate subcolumns in JSON column.

Syntax

Arguments

json — JSON .

Returned value

An array of paths. Array(String) .

Example

JSONDynamicPathsWithTypes ​

Returns the map of dynamic paths that are stored as separate subcolumns and their types in each row in JSON column.

Syntax

Arguments

json — JSON .

Returned value

An array of paths. Map(String, String) .

Example

JSONSharedDataPaths ​

Returns the list of paths that are stored in shared data structure in JSON column.

Syntax

Arguments

json — JSON .

Returned value

An array of paths. Array(String) .

Example

JSONSharedDataPathsWithTypes ​

Returns the map of paths that are stored in shared data structure and their types in each row in JSON column.

Syntax

Arguments

json — JSON .

Returned value