---
{
    "title": "GET_JSON_DOUBLE",
    "language": "en"
}
---

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## get_json_double
### description
#### Syntax

`DOUBLE get_json_double(VARCHAR json_str, VARCHAR json_path)`


Parse and get the floating-point content of the specified path in the JSON string.
Where json_path must start with the $symbol and use. as the path splitter. If the path contains..., double quotation marks can be used to surround it.
Use [] to denote array subscripts, starting at 0.
The content of path cannot contain ",[and].
If the json_string format is incorrect, or the json_path format is incorrect, or matches cannot be found, NULL is returned.

In addition, it is recommended to use the jsonb type and jsonb_extract_XXX function performs the same function.

Exception handling is as follows:
- if the field specified by json_path does not exist, return NULL
- if datatype of the field specified by json_path is not the same with type of json_extract_t, return t if it can be cast to t else NULL

### example

1. Get the value of key as "k1"

```
mysql> SELECT get_json_double('{"k1":1.3, "k2":"2"}', "$.k1");
+-------------------------------------------------+
| get_json_double('{"k1":1.3, "k2":"2"}', '$.k1') |
+-------------------------------------------------+
|                                             1.3 |
+-------------------------------------------------+
```

2. Get the second element of the array whose key is "my. key"

```
mysql> SELECT get_json_double('{"k1":"v1", "my.key":[1.1, 2.2, 3.3]}', '$."my.key"[1]');
+---------------------------------------------------------------------------+
| get_json_double('{"k1":"v1", "my.key":[1.1, 2.2, 3.3]}', '$."my.key"[1]') |
+---------------------------------------------------------------------------+
|                                                                       2.2 |
+---------------------------------------------------------------------------+
```

3. Get the first element in an array whose secondary path is k1. key - > K2
```
mysql> SELECT get_json_double('{"k1.key":{"k2":[1.1, 2.2]}}', '$."k1.key".k2[0]');
+---------------------------------------------------------------------+
| get_json_double('{"k1.key":{"k2":[1.1, 2.2]}}', '$."k1.key".k2[0]') |
+---------------------------------------------------------------------+
|                                                                 1.1 |
+---------------------------------------------------------------------+
```
### keywords
GET_JSON_DOUBLE,GET,JSON,DOUBLE