Getting error while using DYNAMIC SQL

Question

Hi Team,
I am Oracle DBA. I have limited knowledge on PL/SQL. I used below PL/SQL code to drop 50 partitons from one of the table.
I used Dynamic SQL EXECUTE IMMEDIATE to drop partions. But error occured. If I commented EXECUTE IMMEDIATE, procedure executed successfully.
Please suggest me, where i did the mistake. Also please suggest for better code than my code. please find below code and error details.
SQL> ed
Wrote file afiedt.buf
1 DECLARE
2 CURSOR DROP_PARTITON IS select partition_name from user_tab_subpartitions where PARTITION_NAME<='ABCD_2011_04';
3 BEGIN
4 for curr IN DROP_PARTITON LOOP
5 DBMS_output.put_line(curr.partition_name);
6 execute immediate(Alter table Table_Name drop partition curr.partition_name);
7 end loop;
8* END;
SQL> /
execute immediate(Alter table BILLCHRG drop partition curr.partition_name);
ERROR at line 6:
ORA-06550: line 6, column 19:
PLS-00103: Encountered the symbol "ALTER" when expecting one of the following:
( - + case mod new not null others <an identifier>
<a double-quoted delimited-identifier> <a bind variable> avg
count current exists max min prior sql stddev sum variance
execute forall merge time timestamp interval date
<a string literal with character set specification>
<a number> <a single-quoted SQL string> pipe
<an alternatively-quoted string literal with character set specification>
<an alternative
SQL> ed
Wrote file afiedt.buf
1 DECLARE
2 CURSOR DROP_PARTITON IS select partition_name from user_tab_subpartitions where PARTITION_NAME<='ABCD_2011_04';
3 BEGIN
4 for curr IN DROP_PARTITON LOOP
5 DBMS_output.put_line(curr.partition_name);
6 --execute immediate(Alter table TABLE_NAME drop partition curr.partition_name);
7 end loop;
8* END;
SQL> /
ABCD_2009_06
ABCD_2009_06
ABCD_2009_06
BILLCHRG_2011_04
PL/SQL procedure successfully completed.

Answer 1

PL/SQL code runs on the server, inside an Oracle process - thus PL/SQL code cannot dynamically write and display messages to the client. That server process is not connected to any keyboard, mouse or display.
DBMS_OUTPUT can be used. This is a PL/SQL buffer area in that server process that code can write lines of text too. When the server process informs the client that it has completed, the client can now request the contents of the DBMS_OUTPUT buffer and the client can display it on the client device.
This is what set serveroutput on in SQL*Plus does - tell the sqlplus client to request the DBMS_OUTPUT buffer after each Oracle server call made and to display the contents locally.
So to display the SQL command can be done using DBMS_OUTPUT. E.g.
declare
  dropPart varchar2(32767);
begin
  for c in (select...) loop
    dropPart := 'alter table my_tab drop partition '||c.partition_name';
    --// write the SQL command to DBMS_OUTPUT
    DBMS_OUTPUT.put_line( dropPart );
    --// execute the SQL using a begin..end block in order to catch error
    begin
      execute immediate dropPart;
      DBMS_OUTPUT.put_line( 'command completed successfully' );
    exception when OTHERS then
      DBMS_OUTPUT.put_line( 'command failed with: '||SQLERRM(SQLCODE) );
    end;
  end loop;
end;So after this code block has been executed and partitions dropped, sqlplus will display the DBMS_OUTPUT generated by this code block.