Oracle explain plan

1. explain plan set statement_id = 'bad6' for

select a from b;

Then :

2. SELECT cardinality "Rows",

      lpad(' ',level-1)||operation||' '||

      options||' '||object_name "Plan"

 FROM PLAN_TABLE

CONNECT BY prior id = parent_id

       AND prior statement_id = statement_id

 START WITH id = 0

       AND statement_id = 'bad6'

 ORDER BY id;

OR

2. SELECT * FROM TABLE(dbms_xplan.display('PLAN_TABLE','bad6','ALL'));

running external script in oracle sqlplus

SQL> @external.sql

Perl Dollar Dollar ($$)

Do you know what does $$ stand for in Perl?
It's the process id of the current process.

print $$;

will print the process id of the current process.

Oracle finding indexes/indices for a table

Select  index_name, column_name FROM dba_ind_columns where table_name=’EMP’;