JSON_EXTRACT_DOUBLE

Description

JSON_EXTRACT_DOUBLE extracts the field specified by <json_path> from a JSON object and converts it to DOUBLE type.

Syntax

JSON_EXTRACT_DOUBLE(<json_object>, <json_path>)

Parameters

• <json_object>: JSON type, the target parameter to extract from.
• <json_path>: String type, the JSON path to extract the target element from the target JSON.

Return Value

Nullable(DOUBLE) Returns the extracted DOUBLE value, returns NULL in some cases

Usage Notes

1. If <json_object> or <json_path> is NULL, returns NULL.
2. If the element specified by <json_path> does not exist, returns NULL.
3. If the element specified by <json_path> cannot be converted to DOUBLE, returns NULL.
4. Its behavior is consistent with "cast + json_extract", which is equivalent to:
   CAST(JSON_EXTRACT(<json_object>, <json_path>) as DOUBLE)

Examples

1. Normal parameters
   SELECT json_extract_double('{"id": 123.345, "name": "doris"}', '$.id');

   +-----------------------------------------------------------------+
   | json_extract_double('{"id": 123.345, "name": "doris"}', '$.id') |
   +-----------------------------------------------------------------+
   |                                                         123.345 |
   +-----------------------------------------------------------------+

2. Case where path does not exist
   SELECT json_extract_double('{"id": 123.345, "name": "doris"}', '$.id2');

   +------------------------------------------------------------------+
   | json_extract_double('{"id": 123.345, "name": "doris"}', '$.id2') |
   +------------------------------------------------------------------+
   |                                                             NULL |
   +------------------------------------------------------------------+

3. NULL parameters
   SELECT json_extract_double('{"id": 123.345, "name": "doris"}', NULl);

   +---------------------------------------------------------------+
   | json_extract_double('{"id": 123.345, "name": "doris"}', NULl) |
   +---------------------------------------------------------------+
   |                                                          NULL |
   +---------------------------------------------------------------+

   SELECT json_extract_double(NULL, '$.id2');

   +------------------------------------+
   | json_extract_double(NULL, '$.id2') |
   +------------------------------------+
   |                               NULL |
   +------------------------------------+

4. Case where conversion to DOUBLE is not possible
   SELECT json_extract_double('{"id": 123, "name": "doris"}','$.name');

   +--------------------------------------------------------------+
   | json_extract_double('{"id": 123, "name": "doris"}','$.name') |
   +--------------------------------------------------------------+
   |                                                         NULL |
   +--------------------------------------------------------------+