String Binding in plsql

Question

Hi All,
I have two table, the first table(emp) contains few columns LIKE
eno, ename etc. with some data. In my second table(eval1) I
have one column which holds column names of first table ex.
ename. How can I get the column value of first table based on
columns entered in second table. The ex. Which I am trying.
table1 : emp
eno ename sal
1 james 1000
2 bond 2000
table2 : eval1
col1
ename
procedure p1 is
cursor data1 is select * from emp;
cursor c_val is select col1 fromtable2 ;
p_col varchar2(100);
BEGIN
for r_data in data1 loop
     FOR R_VAL IN C_VAL LOOP
BEGIN
     p_col := 'r_data.'||r_val.col1;
     select p_col into p_out from dual ;
     dbms_output.put_line('chr(10) 1 '||p_out);
END;
END LOOP;
END LOOP;
END;
What I am expecting from above code is, the p_out should
return 'james', 'bond'.... for each record. Right not it is just
returning r_data.ename.
Please help me. Thanks in advance.
Swetha.

Answer 1

Hi,
This is a case of Dynamic Sql where u will want to dynamically
create the query.
Create procedure p1 is
    cursor data1 is select * from emp;
    cursor c_val is select col1 fromtable2 ;
    p_col varchar2(100);
BEGIN
    for r_data in data1 loop
      FOR R_VAL IN C_VAL LOOP
      BEGIN
           p_col := 'r_data.'||r_val.col1;
           execute immediate 'select ' || p_col || ' from emp'  
into p_out;
           dbms_output.put_line('chr(10) 1 '||p_out);
       END;
      END LOOP;
    END LOOP;
END;
You can also Ref Cursors.
Regards,
Ganesh R