JSON_EXTRACT
Descriptionβ
JSON_EXTRACT is a series of functions that extract the field specified by json_path from JSON data and provide different series of functions according to the type of the field to be extracted.
- JSON_EXTRACT returns the VARCHAR type for a json string of the VARCHAR type.
- JSON_EXTRACT_ISNULL returns the BOOLEAN type indicating whether it is a json null.
- JSON_EXTRACT_BOOL returns the BOOLEAN type.
- JSON_EXTRACT_INT returns the INT type.
- JSON_EXTRACT_BIGINT returns the BIGINT type.
- JSON_EXTRACT_LARGEINT returns the LARGEINT type.
- JSON_EXTRACT_DOUBLE returns the DOUBLE type.
- JSON_EXTRACT_STRING returns the STRING type.
Aliasβ
- JSONB_EXTRACT is the same as JSON_EXTRACT.
- JSONB_EXTRACT_ISNULL is the same as JSON_EXTRACT_ISNULL.
- JSONB_EXTRACT_BOOL is the same as JSON_EXTRACT_BOOL.
- JSONB_EXTRACT_INT is the same as JSON_EXTRACT_INT.
- JSONB_EXTRACT_BIGINT is the same as JSON_EXTRACT_BIGINT.
- JSONB_EXTRACT_LARGEINT is the same as JSON_EXTRACT_LARGEINT.
- JSONB_EXTRACT_DOUBLE is the same as JSON_EXTRACT_DOUBLE.
- JSONB_EXTRACT_STRING is the same as JSON_EXTRACT_STRING.
Syntaxβ
JSON_EXTRACT (<json_str>, <path>[, path] ...)
JSON_EXTRACT_ISNULL (<json_str>, <path>)
JSON_EXTRACT_BOOL (<json_str>, <path>)
JSON_EXTRACT_INT (<json_str>, <path>)
JSON_EXTRACT_BIGINT (<json_str>, <path>)
JSON_EXTRACT_LARGEINT (<json_str>, <path>)
JSON_EXTRACT_DOUBLE (<json_str>, <path>)
JSON_EXTRACT_STRING (<json_str>, <path>)
Alias functions have the same syntax and usage as the above functions, except for the function names.
Parametersβ
| Parameter | Description |
|---|---|
<json_str> | The JSON-type parameter or field to be extracted. |
<path> | The JSON path to extract the target element from the target JSON. |
| json path syntax: |
- '$' for json document root
- '.k1' for element of json object with key 'k1'
- If the key column value contains ".", double quotes are required in json_path, For example: SELECT json_extract('{"k1.a":"abc","k2":300}', '$."k1.a"');
- '[i]' for element of json array at index i
- Use '$[last]' to get the last element of json_array, and '$[last-1]' to get the penultimate element, and so on.
Return Valuesβ
According to the type of the field to be extracted, return the data type of the specified JSON_PATH in the target JSON. Special case handling is as follows:
- If the field specified by json_path does not exist in the JSON, return NULL.
- If the actual type of the field specified by json_path in the JSON is inconsistent with the type specified by json_extract_t.
- if it can be losslessly converted to the specified type, return the specified type t; if not, return NULL.
Examplesβ
SELECT json_extract('{"id": 123, "name": "doris"}', '$.id');
+------------------------------------------------------+
| json_extract('{"id": 123, "name": "doris"}', '$.id') |
+------------------------------------------------------+
| 123 |
+------------------------------------------------------+
SELECT json_extract('[1, 2, 3]', '$.[1]');
+------------------------------------+
| json_extract('[1, 2, 3]', '$.[1]') |
+------------------------------------+
| 2 |
+------------------------------------+
SELECT json_extract('{"k1": "v1", "k2": { "k21": 6.6, "k22": [1, 2] } }', '$.k1', '$.k2.k21', '$.k2.k22', '$.k2.k22[1]');
+-------------------------------------------------------------------------------------------------------------------+
| json_extract('{"k1": "v1", "k2": { "k21": 6.6, "k22": [1, 2] } }', '$.k1', '$.k2.k21', '$.k2.k22', '$.k2.k22[1]') |
+-------------------------------------------------------------------------------------------------------------------+
| ["v1",6.6,[1,2],2] |
+-------------------------------------------------------------------------------------------------------------------+
SELECT json_extract('{"id": 123, "name": "doris"}', '$.aaa', '$.name');
+-----------------------------------------------------------------+
| json_extract('{"id": 123, "name": "doris"}', '$.aaa', '$.name') |
+-----------------------------------------------------------------+
| [null,"doris"] |
+-----------------------------------------------------------------+
SELECT JSON_EXTRACT_ISNULL('{"id": 123, "name": "doris"}', '$.id');
+----------------------------------------------------------------------------+
| jsonb_extract_isnull(cast('{"id": 123, "name": "doris"}' as JSON), '$.id') |
+----------------------------------------------------------------------------+
| 0 |
+----------------------------------------------------------------------------+
SELECT JSON_EXTRACT_BOOL('{"id": 123, "name": "NULL"}', '$.id');
+-------------------------------------------------------------------------+
| jsonb_extract_bool(cast('{"id": 123, "name": "NULL"}' as JSON), '$.id') |
+-------------------------------------------------------------------------+
| NULL |
+-------------------------------------------------------------------------+
SELECT JSON_EXTRACT_INT('{"id": 123, "name": "NULL"}', '$.id');
+------------------------------------------------------------------------+
| jsonb_extract_int(cast('{"id": 123, "name": "NULL"}' as JSON), '$.id') |
+------------------------------------------------------------------------+
| 123 |
+------------------------------------------------------------------------+
SELECT JSON_EXTRACT_INT('{"id": 123, "name": "doris"}', '$.name');
+---------------------------------------------------------------------------+
| jsonb_extract_int(cast('{"id": 123, "name": "doris"}' as JSON), '$.name') |
+---------------------------------------------------------------------------+
| NULL |
+---------------------------------------------------------------------------+
SELECT JSON_EXTRACT_STRING('{"id": 123, "name": "doris"}', '$.name');
+------------------------------------------------------------------------------+
| jsonb_extract_string(cast('{"id": 123, "name": "doris"}' as JSON), '$.name') |
+------------------------------------------------------------------------------+
| doris |
+------------------------------------------------------------------------------+
