Execute the expression in select statement

Question

CREATE TABLE TEST1
  OFFICE_PRODUCTS     NUMBER,
  OFFICE_ELECTRONICS  NUMBER
Insert into TEST1 (OFFICE_PRODUCTS, OFFICE_ELECTRONICS) Values(1, 0);
COMMIT;
CREATE TABLE TEST2
  EXPORT_FIELD_NAME         VARCHAR2(100 BYTE),
  EXPORT_COLUMN_EXPRESSION  VARCHAR2(100 BYTE)
Insert into TEST2
   (EXPORT_FIELD_NAME, EXPORT_COLUMN_EXPRESSION)
Values ('A1', 'least(OFFICE_PRODUCTS, OFFICE_ELECTRONICS)');
COMMIT; I want to be execute the expression should run in select statement how to do?
and tried as like below,it's not working.
select (select EXPORT_COLUMN_EXPRESSION from test2 where EXPORT_FIELD_NAME='A1') FROM TEST1;

Answer 1

968892 wrote:
CREATE TABLE TEST1
OFFICE_PRODUCTS     NUMBER,
OFFICE_ELECTRONICS  NUMBER
Insert into TEST1 (OFFICE_PRODUCTS, OFFICE_ELECTRONICS) Values(1, 0);
COMMIT;
CREATE TABLE TEST2
EXPORT_FIELD_NAME         VARCHAR2(100 BYTE),
EXPORT_COLUMN_EXPRESSION  VARCHAR2(100 BYTE)
Insert into TEST2
(EXPORT_FIELD_NAME, EXPORT_COLUMN_EXPRESSION)
Values ('A1', 'least(OFFICE_PRODUCTS, OFFICE_ELECTRONICS)');
COMMIT; I want to be execute the expression should run in select statement how to do?
and tried as like below,it's not working.
select (select EXPORT_COLUMN_EXPRESSION from test2 where EXPORT_FIELD_NAME='A1') FROM TEST1;
Your problems are many...
a) it's very poor design to be storing expressions or sql statements or any 'executable' style code as data in the database.
b) what you're storing is a string of characters. Oracle isn't going to miraculously know that that is some expression that has to be evaluated, so why should it decide to treat it as such?
c) this poor design can lead to security issues especially around SQL injection.
d) to actually perform what you want would require you to build a dynamic SQL statement and then execute that using EXECUTE IMMEDIATE or DBMS_SQL (or for a 3rd party client, a Ref Cursor), but then there are numerous issues around doing dynamic SQL, aside from SQL injection, in that you are producing code that is not validated at compile time and can thus lead to bugs showing only at run-time and sometime only under certain conditions; the code is harder to maintain; the code can potentially be avoiding the use of bind variables, impacting on resources and performance on the database; the final query can be difficult to know just from reading the code, making further development or debugging a pain in the posterior. Essentially, dynamic SQL is considered very poor design and is 99.9% of the time used for the wrong reasons.
So, why are you trying to do this? What is the business requirement you are trying to solve?