Table design for multi-type data
Not sure why one of the answers made such bold statement .
Regardless: everything can be modeled in relational model

create table entry 
( 
  id number(12) primary key, 
  name varchar2(256) not null unique,  
  customer_id number not null references customer(id)
);

create table datatypes
(
 id number primary key,
 name varchar2(256) not null unique
);
create table entry_data ( 
  id number(12) primary key, 
  datatype_id  number not null references datatypes(id),
  value     varchar2(256),  --or CLOB ,no index
  value_geometry geom  ,    -- no index
  --value_blob   blob -- if you neeed, no index
  entry_id number not null references entry(id),
);


your task is related to the multi-valued attributes task.
Datatypes table will abstract your datatypes, however 2 value** columns are created in entry_data due to the fact that your data can be different in nature(belong to different Classes), thus would need different storage. But as far as varchar2 vs. number vs.date -- all can be placed into varchar2 , just would need later on some casting. And with very simplistic logic of NVL in code you can determine which column was populated out of value or value_geometry.