Reg: Including an expression in query

Question

Hi All,
i have a table with two fields like id and expr.
id is unique.
And expr contains expressions like
FirstName||' '||MiddleName||' '||LastName etc ..
My requirement is i have to write a query to fetch employee information from employee table along with full name by embedding/executing the above expression.
I can write like this
Select Employee.*,FirstName||' '||MiddleName||' '||LastName as "Full Name" from Employee.
But here i know the id value only not the expression itself.
Select Employee.*,(select Expr from expr_table where id=<id_value>) AS "First Name" from Employee
It is giving the expression itself instead of executing the expression. It is considering it as a string i think.
Please suggest me anyone in this regards.
Thanks in advance,
Anil Kumar Ch.

Answer 1

Hi, I dont know how to do it SQL, but you can do it in PL/SQL using EXECUTE IMMEDIATE statement .
BEGIN
select Expr INTO v_expr from expr_table where id=<id_value>;
EXECUTE IMMEDIATE 'SELECT ' || v_expr || ' FROM EMPLOYEE' INTO v_full_name ;
dbms_output.put_line(v_full_name);
END;