mysql - Can't detect null value from JSON_EXTRACT

Question

I have a database that has an array of data stored in a JSON column. I need to find all values that have a null value at a particular position in the JSON array. While pulling out the data with JSON_EXTRACT seemed trivial, none of my comparisons to null have worked, all of them claiming the value is null.

Here is the example code that should work as far as I can tell:

SELECT JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]') , (JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]') is null)
FROM ate.readings_columns_new;

The first few rows of my results table look like this:

null                    |   0
"INTERNALTEMPERATURE"   |   0
"INPUT_VOLTAGE"         |   0
null                    |   0
null                    |   0
"AH1"                   |   0

I have tried every comparison I can think of, and they all result in a 0:

(JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]') is null)
(JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]') <=> null)
ISNULL(JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]'))
(JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]') <=> 'null')

Is there some key to comparing null values pulled from a JSON_EXTRACT?

Answer 1

SELECT 
  JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]'), 
  (JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]') = CAST('null' AS JSON))
FROM ate.readings_columns_new;

or

SELECT 
  JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]'), 
  (JSON_TYPE(JSON_EXTRACT(`COLUMNS_HEADERS`, '$[1]')) = 'NULL')
FROM ate.readings_columns_new;

See the docs for JSON_TYPE.