Accessing record fields by their name in Oracle - oracle

Question

I want to know if there exists something like Reflection API in PL/SQL or not.
I have a table like
create table my_table (
id number,
value1 number,
value2 number,
value3 number,
value4 number,
value5 number);
And I have a variable as
rec as my_table%rowtype
... fill rec
insert into my_table values rec;
is there any way I can populate rec field dynamically by its name.
I mean I know the index (in this case something between 1 and 5), so I want to set 'value'||index to something.
As in my real case the last index is much more than 5, using a set of if/elsif is not proper. By the way number of fields is increased in long term (for example value6, value7 ma be added next year and so on, so I wan to write some kind of code not to be changed on every new column).

Answer 1

You can access variables in a program using dynamic SQL only if they are available globally. If you declare you record in the spec you can build utility functions that will use EXECUTE IMMEDIATE to build a small PL/SQL block to set the value. Here is a simple example of what you are looking for. Notice you can overload the set procedure to keep your datatypes intact.
CREATE TABLE my_table (
value1 NUMBER,
value2 VARCHAR2(100),
value3 DATE);
CREATE OR REPLACE PACKAGE pkg_my_table IS
my_table_rec my_table%ROWTYPE;
FUNCTION build_statement(i_record IN VARCHAR2,
i_field IN VARCHAR2) RETURN VARCHAR2;
PROCEDURE set_value(i_record IN VARCHAR2,
i_field IN VARCHAR2,
i_value IN VARCHAR2);
PROCEDURE set_value(i_record IN VARCHAR2,
i_field IN VARCHAR2,
i_value IN NUMBER);
PROCEDURE set_value(i_record IN VARCHAR2,
i_field IN VARCHAR2,
i_value IN DATE);
PROCEDURE insert_a_row;
END pkg_my_table;
/
CREATE OR REPLACE PACKAGE BODY pkg_my_table IS
FUNCTION build_statement(i_record IN VARCHAR2,
i_field IN VARCHAR2) RETURN VARCHAR2 IS
BEGIN
RETURN 'BEGIN ' || lower($$PLSQL_UNIT) || '.' || i_record || '.' || i_field || ' := :x; END;';
END build_statement;
PROCEDURE set_value(i_record IN VARCHAR2,
i_field IN VARCHAR2,
i_value IN VARCHAR2) IS
BEGIN
EXECUTE IMMEDIATE build_statement(i_record => i_record,
i_field => i_field)
USING i_value;
END set_value;
PROCEDURE set_value(i_record IN VARCHAR2,
i_field IN VARCHAR2,
i_value IN NUMBER) IS
BEGIN
EXECUTE IMMEDIATE build_statement(i_record => i_record,
i_field => i_field)
USING i_value;
END set_value;
PROCEDURE set_value(i_record IN VARCHAR2,
i_field IN VARCHAR2,
i_value IN DATE) IS
BEGIN
EXECUTE IMMEDIATE build_statement(i_record => i_record,
i_field => i_field)
USING i_value;
END set_value;
PROCEDURE insert_a_row IS
BEGIN
my_table_rec := NULL;
set_value(i_record => 'my_table_rec',
i_field => 'value1',
i_value => 42);
set_value(i_record => 'my_table_rec',
i_field => 'value2',
i_value => 'forty-two');
set_value(i_record => 'my_table_rec',
i_field => 'value3',
i_value => to_date('1/1/1942',
'mm/dd/yyyy'));
INSERT INTO my_table
VALUES my_table_rec;
END insert_a_row;
END pkg_my_table;
/
BEGIN
pkg_my_table.insert_a_row;
END;
/
SELECT *
FROM my_table;
-- 42 forty-two 1/1/1942
Beware globals: you need to reset them correctly before using them again or you might get data carried over from previous invocations. Setting an entire record type variable to NULL will reset all the underlying fields (handy).
You will also be prone to ORA-04068: existing state of packages has been discarded errors should you compile PL/SQL with globals where there are active sessions referencing your code. Generally this is not a problem, but it is a behavioral difference.