Doubt in select in to statement

Question

In employees table employee_id first_name last_name are columns.
Written Following pl/sql and it compiles fine
create or replace procedure passEmp(employee_id number,colname varchar2)
as
sname varchar2(50);
begin
select colname into sname from employees where employee_id=100;
dbms_output.put_line(colname ||'value for '||employee_id ||' is '||sname);
end;
When I execute above procedure as
execute passEmp(100,'last_name');
Output is
last_name value for 100 is last_name.
What I am expecting is since I am passing colname as last_name
it should give last_name of employee 100.
Can any one explain why it won't return last_name of employee 100.
When I execute above procedure as
execute passEmp(100,'last_names');---- last_names column is not at all there in table.
Output is
last_names value for 100 is last_names.
Why the procedure is running with out error even when I am passing last_names as
argument which is not existing in table at all....

Answer 1

Hi,
Try this.
create or replace procedure passEmp(employee_id number,colname varchar2)
as
    sname varchar2(50);
    v_sql   varchar2(100);
begin
    v_sql := 'select ' || colname || ' from employees where employee_id = '|| employee_id;
    execute immediate v_sql into sname;
    dbms_output.put_line(colname ||'value for '||employee_id ||' is '||sname);
end;
show errorsIf you want to pass column names or table name at a run time, then normal select won't work.
In that scenario you should use dynamic sql.