SQL query with seq and select

INSERT INTO table (id, scnd_id, thrd_id, date_act)
VALUES(
    SOME_SEQ.nextval,  
    (SELECT
         t2.scnd_id,
         t2.thrd_id,
         MAX(t3.ppn_dt)
    FROM table2
        LEFT JOIN table3 t3
            ON t2.thrd_id = t3.thrd_id
    GROUP BY t2.thrd_id, t2.scnd_id));

SQL error:

> ORA-00936: missing expression

I need to insert id from seq and data from select query

How to fix it?

Like this:

insert into table (id, scnd_id, thrd_id, date_act)
select some_seq.nextval,
  x.scnd_id,
  x.thrd_id, 
  x.ppn_dt
from (select 
        t2.scnd_id, 
        t2.thrd_id,
        max(t3.ppn_dt) ppn_dt
      from table2 t2 left join table3 t3 on t2.thrd_id = t3.thrd_id
      group by t2.thrd_id, t2.scnd_id
     ) x;

You can create a trigger before insert table and when id is null put the sequence.nexval

CREATE OR REPLACE TRIGGER "T_I_TABLE"
  BEFORE INSERT ON TABLE
  FOR EACH ROW
BEGIN
  --
  IF inserting THEN
  
    IF :new.id IS NULL THEN
      :new.id := SOME_SEQ.nextval;
    END IF;
    --
  END IF;
  --
END T_I_TABLE;

Then your insert can be this:

INSERT INTO TABLE
  (scnd_id, thrd_id, date_act)
  (SELECT t2.scnd_id, t2.thrd_id, MAX(t3.ppn_dt)
     FROM table2
     LEFT JOIN table3 t3
       ON t2.thrd_id = t3.thrd_id
    GROUP BY t2.thrd_id, t2.scnd_id);