Using Variables in SQL*PLUS

Question

Hi,
I hope to get any insight possible. I am using External tables and the Default directory is set. Now the process is that I get an automatic downloads of files placed in that directory. They are all to have the same naming system.
Test_June_2006 or Test_July_2006 and so on. Basically the month will be one behind, so Since it is August, I am looking for Test_July_2006.
I was able to set the "location" parameter to accept a variable, but i am having some trouble with set the value to that variable.
My code:
define month = EXTRACT(MONTH FROM CURRENT_DATE)-1||'_'||EXTRACT(YEAR FROM CURRENT_DATE).txt
variable month varchar2(100)
drop table ext_Test;
create table ext_Test
(field1      varchar2(25),
field2      varchar2(10),
field3     varchar2(10),
field4 varchar2(15),
field5 Float,
field6     Float,
field7 Float
organization external
( default directory sourcedata
access parameters
( records delimited by newline
SKIP 1
fields terminated by ','
OPTIONALLY ENCLOSED BY '"'
missing field values are null
location ('Test_&month')
reject limit 0;
When I tried "location ('&month') and setting month to July, it worked fine, but now that I am adding functions, it is not setting the variable properly.
Any help would be appreciated. Thank you.

Answer 1

You cannot use & substitution variable to replace file name dynamically.
You will have to use the ALTER TABLE command at run time to alter the location of the file to what you want before you start processing.
SQL> create table ext_Test
  2  (field1 varchar2(25),
  3  field2 varchar2(10),
  4  field3 varchar2(10),
  5  field4 varchar2(15),
  6  field5 Float,
  7  field6 Float,
  8  field7 Float
  9  )
10  organization external
11  ( default directory sourcedata
12  access parameters
13  ( records delimited by newline
14  SKIP 1
15  fields terminated by ','
16  OPTIONALLY ENCLOSED BY '"'
17  missing field values are null
18  )
19  location ('Test_&month')
20  )
21  reject limit 0;
Enter value for month: july
old  19: location ('Test_&month')
new  19: location ('Test_july')
Table created.
SQL> alter table ext_test location('Test_August') ;
Table altered.
SQL>