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How to use the Type TOraReference or Type ref for post in Query?

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Hi, my problem is: I have 2 tables, 1 with the reference of other.
Exemple:
create type course_t as object
(
course_name varchar(20)
...
);
create table tb_course of course_t;

Create type peoble as object
(
cod Integer,
name varchar(20),
course ref course_t
);

create table tb_peoble of peoble;


I need to record the field type course with the reference.

My Code.

...
querypeoblecourse :TOrareferencefield;
...

query.sql.text := 'select ref(a) from tb_course where course_name = ''...'''

querypeoblecourse.assign(query.fields[0]);
querypeoble.post;

but it generates an error

You can't modify REF fields in SELECT query. To assing value to REF field you can write INSERT or UPDATE query with parameter of type 'Reference'.
To get value from REF field you can use GetRef(FieldName) method of TOraDataSet.

Examle:
query.sql.text := 'select ref(a) REF_A from tb_course where course_name = ''...''';
query.open;

OraSQLUpdate.SQL.Text :=
'UPDATE tb_peoble SET COURSE = :COURSE WHERE COD = :COD';

OraSQLUpdate.ParamByName('cod').AsInteger := 1;
OraSQLUpdate.ParamByName('COURSE').AsRef := query.GetRef('REF_A');
OraSQLUpdate.Execute;

Tks challenger!! you it helped me sufficiently.