ClickHouse/docs/en/sql-reference/aggregate-functions/reference/distinctjsonpaths.md

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distinctJSONPaths

Calculates the list of distinct paths stored in JSON column.

Syntax

distinctJSONPaths(json)

Arguments

• json — JSON column.

Returned Value

• The sorted list of paths Array(String).

Example

Query:

DROP TABLE IF EXISTS test_json;
CREATE TABLE test_json(json JSON) ENGINE = Memory;
INSERT INTO test_json VALUES ('{"a" : 42, "b" : "Hello"}'), ('{"b" : [1, 2, 3], "c" : {"d" : {"e" : "2020-01-01"}}}'), ('{"a" : 43, "c" : {"d" : {"f" : [{"g" : 42}]}}}')

SELECT distinctJSONPaths(json) FROM test_json;

Result:

┌─distinctJSONPaths(json)───┐
│ ['a','b','c.d.e','c.d.f'] │
└───────────────────────────┘

distinctJSONPathsAndTypes

Calculates the list of distinct paths and their types stored in JSON column.

Syntax

distinctJSONPathsAndTypes(json)

Arguments

• json — JSON column.

Returned Value

• The sorted map of paths and types Map(String, Array(String)).

Example

Query:

DROP TABLE IF EXISTS test_json;
CREATE TABLE test_json(json JSON) ENGINE = Memory;
INSERT INTO test_json VALUES ('{"a" : 42, "b" : "Hello"}'), ('{"b" : [1, 2, 3], "c" : {"d" : {"e" : "2020-01-01"}}}'), ('{"a" : 43, "c" : {"d" : {"f" : [{"g" : 42}]}}}')

SELECT distinctJSONPathsAndTypes(json) FROM test_json;

Result:

┌─distinctJSONPathsAndTypes(json)───────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ {'a':['Int64'],'b':['Array(Nullable(Int64))','String'],'c.d.e':['Date'],'c.d.f':['Array(JSON(max_dynamic_types=16, max_dynamic_paths=256))']} │
└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

Note

If JSON declaration contains paths with specified types, these paths will be always included in the result of distinctJSONPaths/distinctJSONPathsAndTypes functions even if input data didn't have values for these paths.

DROP TABLE IF EXISTS test_json;
CREATE TABLE test_json(json JSON(a UInt32)) ENGINE = Memory;
INSERT INTO test_json VALUES ('{"b" : "Hello"}'), ('{"b" : "World", "c" : [1, 2, 3]}');

SELECT json FROM test_json;

┌─json──────────────────────────────────┐
│ {"a":0,"b":"Hello"}                   │
│ {"a":0,"b":"World","c":["1","2","3"]} │
└───────────────────────────────────────┘

SELECT distinctJSONPaths(json) FROM test_json;

┌─distinctJSONPaths(json)─┐
│ ['a','b','c']           │
└─────────────────────────┘

SELECT distinctJSONPathsAndTypes(json) FROM test_json;

┌─distinctJSONPathsAndTypes(json)────────────────────────────────┐
│ {'a':['UInt32'],'b':['String'],'c':['Array(Nullable(Int64))']} │
└────────────────────────────────────────────────────────────────┘