sql - Transpose select results with Oracle

Question

my question is, with some background:

I have to generate some sql queries based on the table metadata (column format), and the result is something like:

TABLENAME1|COL1
TABLENAME1|COL2
TABLENAME2|COL1
TABLENAME2|COL2
TABLENAME2|COL3
TABLENAME3|COL1
TABLENAME4|COL1
TABLENAME4|COL2
... /*some other 1800 rows */

(Yeah, it's ordered.) What I need is to transpose this data, based on the first column, so the expected output would be:

TABLENAME1|COL1|COL2|NULL
TABLENAME2|COL1|COL2|COL3
TABLENAME3|COL1|NULL|NULL
TABLENAME4|COL1|COL2|NULL
/* less then 1800 rows ;-) */

Is it possible using Oracle SQL?

Thanks in advance!

Answer 1

If you want to generate the query for each call or use a hardcoded max-column-count, then you can do something like that:

WITH tab AS
(
  SELECT table_name, column_name FROM user_tab_cols WHERE column_id <= 4
) -- user_tab_cols used to provide test data, use your table instead
SELECT MAX(c1) c1,
       MAX(c2) c2,
       MAX(c3) c3,
       MAX(c4) c4
  FROM (SELECT table_name,
               DECODE( column_id, 1, column_name ) c1,
               DECODE( column_id, 2, column_name ) c2,
               DECODE( column_id, 3, column_name ) c3,
               DECODE( column_id, 4, column_name ) c4
          FROM ( SELECT table_name,
                        column_name,
                        ROW_NUMBER() OVER ( PARTITION BY table_name ORDER BY column_name ) column_id
                   FROM tab
               )
       )
 GROUP BY table_name
 ORDER BY table_name

---

If it is sufficient to get it in that form

TABLENAME1|COL1,COL2
TABLENAME2|COL1,COL2,COL3

have a look at Tom Kyte's stragg.