Exclude columns with no data in them - sql

Question

Using Oracle with TOAD.
I have a table that looks something like this (columns 2 and 4 are empty and columns 1, 3 and 5 have data in them):
column_1 column_2 column_3 column_4 column_5
a1 b1 c1
a2 b2 c2
a3 b3 c3
a4 b4 c4
I would like to do a simple select that excludes columns with no data in them (= columns 2 and 4) or ain other words, to select only the columns that have data in them.
Is there a select command such as SELECT * FROM test_table WHERE columns ARE NOT NULL (this is pseudo code just for clarification for my problem).
The result should look like this:
column_1 column_3 column_5
a1 b1 c1
a2 b2 c2
a3 b3 c3
a4 b4 c4

Answer 1

You have to do a three-step approach but it is largely tedious but do-able in sqlplus
1)First identify the columns which are empty
2)Define the headers without those columns
3)define the body without those columns
WITH data AS
(
SELECT '1' a,
'' b ,
2 c ,
'' d,
5 e
FROM dual
UNION ALL
SELECT '7' a,
'' b ,
2 c ,
'' d,
6
FROM dual
UNION ALL
SELECT '3' a,
'' b ,
3 c ,
'' d,
7
FROM dual
UNION ALL
SELECT '4' a,
'' b ,
3 c ,
'' d,
8
FROM dual
UNION ALL
SELECT '5' a,
'' b ,
2 c ,
'' d,
9
FROM dual),d1 AS
(
SELECT First_value(a) ignore nulls over (PARTITION BY a ORDER BY ROWNUM) ca,
first_value(b) ignore nulls over (PARTITION BY b ORDER BY ROWNUM) cb,
first_value(c) ignore nulls over (PARTITION BY c ORDER BY ROWNUM) cc,
first_value(d) ignore nulls over (PARTITION BY d ORDER BY ROWNUM) cd,
first_value(e) ignore nulls over (PARTITION BY e ORDER BY ROWNUM) ce
FROM data
WHERE ROWNUM=1 ),
d2 as (SELECT 0 rw,
CASE
WHEN ca IS NOT NULL THEN 'a'
ELSE ''
END
||chr(9)
||
CASE
WHEN cb IS NOT NULL THEN 'b'
ELSE ''
END
||chr(9)
||
CASE
WHEN cc IS NOT NULL THEN 'c'
ELSE ''
END
||chr(9)
||
CASE
WHEN cd IS NOT NULL THEN 'd'
ELSE ''
END
||chr(9)
||
CASE
WHEN ce IS NOT NULL THEN 'e'
ELSE ''
END as DATA1
FROM d1
UNION ALL
SELECT
rownum rw,
a
||chr(9)
||b
||chr(9)
||c
||chr(9)
||d
||chr(9)
||e
FROM data)
select /*ansiconsole*/ DATA1
from d2 order by rw asc;