create table my_test (i varchar2(1))

insert into my_test (i) 
select '1' from dual 
union 
select '5' from dual 
union 
select '7' from dual

commit

declare  
    p_input_json varchar2(1000); 
    vCount int; 
     
begin 
    select json_arrayagg(X format json returning varchar2(1000)) 
        into p_input_json 
    from ( 
        select '1' as X from dual 
        union 
        select '2' from dual 
        union 
        select '3' from dual 
        ); 
         
    DBMS_OUTPUT.put_line (p_input_json);  
     
    with jdata as ( 
        select treat(p_input_json as json) as jrow 
        from dual 
        ) 
    select count(*) 
        into vCount 
    from my_test 
        where i in ( 
            select jrow --jrow.? 
            from jdata 
            ); 
     
    DBMS_OUTPUT.put_line (vCount);  
end; 

drop table my_test