Oracle PL/SQL Programming: A Developer's Workbook

Expert

Q:
13-18.	The first EXECUTE IMMEDIATE is the correct one. NDS associates placeholders in a SQL statement with bind arguments in the USING clause by position, not by name. Therefore, you must repeat the bind value for each appearance of the same placeholder in your string.
Q:
13-19.	The implementation seems straightforward enough: /* Filename on web page: value_in.sf */ CREATE OR REPLACE FUNCTION value_in ( varname IN VARCHAR ) RETURN VARCHAR2 IS retval VARCHAR2(2000); BEGIN EXECUTE IMMEDIATE 'BEGIN :val := ' || varname || '; END;' USING OUT retval; RETURN retval; END; / You probably had to experiment, however, with a few approaches before you got it to work properly. I did. I tried this EXECUTE IMMEDIATE first: EXECUTE IMMEDIATE 'BEGIN :val := :varname; END;' USING OUT retval, varname; But when I executed the function I got these results: SQL> exec DBMS_OUTPUT.PUT_LINE (value_in('p.linelen')) p.linelen In other words, it did not evaluate what is in this case a function call. It simply treated it as a literal string. I realized that I needed to concatenate the variable name into the string so that it would be evaluated when the dynamic PL/SQL block was executed.
Q:
13-20.	When this code is executed with the logic shown in the problem, you get this error: PLS-00201: identifier 'N' must be declared The problem is that when you execute a dynamic PL/SQL block, it executes in “global” scope. Within that string you can reference only data elements that are globally available, which means they are ...