用双引号包起来

select * from tb where json_str = '"null"'

select * from 24ke_work_task where json =json_array() or json is null 如果是json 里面的字段 要这样 json->'$.field' = json_array()

select * from tb where JSON_CONTAINS(`sport`, 'null');
select * from tb where JSON_CONTAINS(`sport`, 'null', '$');

SELECT * FROM tb WHERE JSON_TYPE(sport) = 'NULL'

select * from tb where JSON_TYPE(sport) is NULL

select * from tb where JSON_DEPTH(sport) = 1