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JSON_ARRAY_LENGTH function

PDFRSS

Note

JSON_PARSE and its associated functions parse JSON values as SUPER, which Amazon Redshift parses more efficiently than VARCHAR.

Instead of using JSON_ARRAY_LENGTH, we recommend that you parse your JSON strings using the JSON_PARSE function to get a SUPER value. Then, use the get_array_length function to get the length of your array.

The JSON_ARRAY_LENGTH function returns the number of elements in the outer array of a JSON string. If the null_if_invalid argument is set to true and the JSON string is invalid, the function returns NULL instead of returning an error.

For more information, see JSON functions.

Syntax

JSON_ARRAY_LENGTH('json_array' [, null_if_invalid ] ) 

Arguments

json_array

A properly formatted JSON array.

null_if_invalid

(Optional) A BOOLEAN value that specifies whether to return NULL if the input JSON string is invalid instead of returning an error. To return NULL if the JSON is invalid, specify true (t). To return an error if the JSON is invalid, specify false (f). The default is false.

Return type

INTEGER

Examples

To return the number of elements in the array, use the following example.

SELECT JSON_ARRAY_LENGTH('[11,12,13,{"f1":21,"f2":[25,26]},14]'); 

+-------------------+
| json_array_length |
+-------------------+
|                 5 |
+-------------------+

To return an error because the JSON is invalid, use the following example.

SELECT JSON_ARRAY_LENGTH('[11,12,13,{"f1":21,"f2":[25,26]},14');
 
ERROR: invalid json array object [11,12,13,{"f1":21,"f2":[25,26]},14

To set null_if_invalid to true, so the statement the returns NULL instead of returning an error for invalid JSON, use the following example.

SELECT JSON_ARRAY_LENGTH('[11,12,13,{"f1":21,"f2":[25,26]},14',true);

+-------------------+
| json_array_length |
+-------------------+
| NULL              |
+-------------------+