title: ORA-00936: missing expression error when inserting values
body: <p>I spend lot of time searching where i made the mistake but i was unable to find it when its going to insert the last record there is a error message showing "ORA-00936: missing expression" How to solve this please help me </p>
  
  <pre><code>create type pearson_types as object(
  name varchar2(50),
  sysID char(6)
  )NOT FINAL;
  
  create type doctor_types under pearson_types(
  regNo char(10),
  specialization varchar2(25)
  )
  
  create table doctor of doctor_types(
  regNo primary key 
  )
  
  create type hospVisits_types as object(
  hosChg float,
  vDate varchar2(20),
  refDoc REF doctor_types,
  docChg float
  )
  
  create type hospvisits_tbl_types as table of hospVisits_types
  
  create type phone_arr as VARRAY(3) of char(10)
  
  create type patient_types under pearson_types
  (
  id char(10),
  dob varchar(20),
  phone phone_arr,
  hospVisits hospvisits_tbl_types
  )
  
  create table patients of patient_types(
  id primary key
  )nested table hospVisits store as Hospital_tables
  
  alter table Hospital_tables add scope for (refDoc) is doctor
  
  insert into doctor values ('Dr.k.perera','D001','1223441234','Gynecologist');
  insert into doctor values ('Dr.p.weerasingha','D002','1234421131','Dermatalogist');
  insert into doctor values ('Prof .S. Fernando','D003','2342111322','Pediatrician');
  insert into doctor values ('Dr.k.Sathgunanathan','D004','2344114344','Pediatrician');
  
  
  insert into patients values('Sampath Weerasingha','P001','732821122V','23-JAN-73',phone_arr('0332124222'),hospvisits_tbl_types(hospVisits_types(50.00,'24-MAY-06',select ref (a) from doctor a where a.regNo='1223441234',500.00)))
  </code></pre>