PL/SQL file writing with generic input - oracle

Question

I recently created a PL/SQL program that creates five different pipe delimited files from related data in a database.
I could not find a way to dynamically pull different tabular data in this case cursors, into a generic procedure that would create the files.
Instead I had to create five separate procedures, one for each file, that took in five different cursors, one for each file requirement record selection.
I can't help but think that there has to be a better way. I was looking into reference cursors but I don't think they are exactly what I am looking for.
How can I achieve this in PL/SQL?
I think what I am looking for is some generic type that can take any data from a cursor given any amount of records and record columns and have the ability to query itself to find what data is in it.

Answer 1

Pass the cursor into your procedure as a SYS_REFCURSOR. Then, use DBMS_SQL.TO_CURSOR_NUMBER(); to convert the ref cursor to a DBMS_SQL cursor.
Then, use DBMS_SQL.DESCRIBE_COLUMNS to figure out the columns in the cursor and DBMS_SQL.DEFINE_COLUMN, DBMS_SQL.FETCH_ROWS and DBMS_SQL.VALUE to get the data from the cursor into PL/SQL variables. Then, write your PL/SQL variables to your output file.
Here's some code that puts all that together for you.
DECLARE
l_rc SYS_REFCURSOR;
PROCEDURE dump_cursor (p_rc IN OUT SYS_REFCURSOR) IS
-- Dump the results of p_rc to log
l_cursor INTEGER;
l_column_count INTEGER;
l_column_descriptions SYS.DBMS_SQL.desc_tab;
l_status INTEGER;
l_column_value VARCHAR2 (4000);
l_column_width NUMBER;
l_rec_count NUMBER := 0;
l_line VARCHAR2 (4000);
FUNCTION get_length (l_column_def IN SYS.DBMS_SQL.desc_rec)
RETURN NUMBER IS
l_width NUMBER;
BEGIN
l_width := l_column_def.col_max_len;
l_width := CASE l_column_def.col_type WHEN 12 THEN /* DATE */
20 WHEN 2 THEN /* NUMBER */
10 ELSE l_width END;
-- Don't display more than 256 characters of any one column (this was my requirement -- your file writer probably doesn't need to do this
l_width := LEAST (256, GREATEST (l_width, l_column_def.col_name_len));
RETURN l_width;
END get_length;
BEGIN
-- This is the date format that I want to use for dates in my output
EXECUTE IMMEDIATE 'alter session set nls_date_format=''DD-MON-YYYY HH24:MI:SS''';
l_cursor := sys.DBMS_SQL.to_cursor_number (p_rc);
-- Describe columns
sys.DBMS_SQL.describe_columns (c => l_cursor, col_cnt => l_column_count, desc_t => l_column_descriptions);
l_line := '';
FOR i IN 1 .. l_column_count LOOP
l_column_width := get_length (l_column_descriptions (i));
l_line := l_line || RPAD (l_column_descriptions (i).col_name, l_column_width);
l_line := l_line || ' ';
DBMS_SQL.define_column (l_cursor,
i,
l_column_value,
4000);
END LOOP;
DBMS_OUTPUT.put_line (l_line);
l_line := '';
FOR i IN 1 .. l_column_count LOOP
l_column_width := get_length (l_column_descriptions (i));
l_line := l_line || RPAD ('-', l_column_width, '-');
l_line := l_line || ' ';
DBMS_SQL.define_column (l_cursor,
i,
l_column_value,
4000);
END LOOP;
DBMS_OUTPUT.put_line (l_line);
-- l_status := sys.DBMS_SQL.execute (l_cursor);
WHILE (sys.DBMS_SQL.fetch_rows (l_cursor) > 0) LOOP
l_rec_count := l_rec_count + 1;
l_line := '';
FOR i IN 1 .. l_column_count LOOP
DBMS_SQL.COLUMN_VALUE (l_cursor, i, l_column_value);
l_column_value := TRANSLATE (l_column_value, CHR (10), CHR (200));
l_column_width := get_length (l_column_descriptions (i));
IF l_column_value IS NULL THEN
l_line := l_line || RPAD (' ', l_column_width);
ELSE
l_line := l_line || RPAD (l_column_value, l_column_width);
END IF;
l_line := l_line || ' ';
END LOOP;
DBMS_OUTPUT.put_line (l_line);
END LOOP;
IF l_rec_count = 0 THEN
DBMS_OUTPUT.put_line ('No data found.');
ELSE
DBMS_OUTPUT.put_line (l_rec_count || ' rows returned.');
END IF;
sys.DBMS_SQL.close_cursor (l_cursor);
-- It would be better to store the current NLS_DATE_FORMAT on entry and restore it here, instead of assuming that it was
-- set to DD-MON-YYYY.
EXECUTE IMMEDIATE 'alter session set nls_date_format=''DD-MON-YYYY''';
EXCEPTION
WHEN OTHERS THEN
EXECUTE IMMEDIATE 'alter session set nls_date_format=''DD-MON-YYYY''';
-- Add your own handling here.
END dump_cursor;
-- Tester code, make sure server output is on
BEGIN
OPEN l_rc FOR 'SELECT object_id, object_name, object_type FROM dba_objects WHERE rownum <= 15';
dump_cursor(l_rc);
END;