Postgres查询以返回其中json列中json包含多个数组元素的行

Question

We are using Postgres DB , in that we have one table contains column of type JSON , format is like below

{
  "name" : "XXX",
  "id"  : "123",
  "course" :[
     {
       "name" : "java",
       "tutor":"YYYY"
     },
     {
       "name" : "python",
       "tutor":"ZZZZ"
     }

   ]  

}


{
  "name" : "XXX",
  "id"  : "123",
  "course" :[
     {
       "name" : "java",
       "tutor":"YYYY"
     },
     {
       "name" : "python",
       "tutor":"ZZZZ"
     }

   ]  

}

like this for example we have two rows , and in the json column we have each like above

i want to Postgre query , which will check the number of elements in the course array and if it is more than one , then only return that row

am not getting how to count the array elements from inside the json key

can any please suggest

Answer 1

why not just json_array_length ?.. eg:

f=# with c(j) as (values('{
  "name" : "XXX",
  "id"  : "123",
  "course" :[
     {
       "name" : "java",
       "tutor":"YYYY"
     },
     {
       "name" : "python",
       "tutor":"ZZZZ"
     }

   ]

}'::json))
select json_array_length(j->'course') from c;
 json_array_length
-------------------
                 2
(1 row)

so smth like

select * from table_name where json_array_length(j->'course') > 1