convert row data into column in oracle [duplicate] - sql

Question

This question already has answers here:
Dynamic Pivot in Oracle's SQL
(10 answers)
Closed 4 years ago.
I have a table mapping which has column code and values as shown below.
A
B
C
D
i want to convert this row level data into columns like
column1 column2 column3 column4
A B C D
Can any one please help here.
Also i don't want to hard code my table data in the query as data might be different every day.

Answer 1

If you want to have a query that gives you a variable number of columns, a way could be dynamic SQL; for example, this query will build a query that does the job, no matter the number of records:
select
'select *
from
mapping
pivot ( max(code) for code in (' ||
listagg('''' || code || ''' AS column' || n, ',') within group (order by code) ||
'))'
from (select code, rownum n from mapping)
this gives this query:
select *
from
mapping
pivot ( max(code) for code in ('A' AS column1,'B' AS column2,'C' AS column3,'D' AS column4))
which gives:
COLUMN1 COLUMN2 COLUMN3 COLUMN4
------- ------- ------- -------
A B C D
1 row selected.
Now the issue is how would you use this; you can run a dynamic query with execute immediate, but here you don't know in advance the number of columns, so you can not fetch the result of this query into anything.
A different approach could be by generating an XML result, for example:
select
dbms_xmlgen.getxml(
'select *
from
mapping
pivot ( max(code) for code in (' ||
listagg('''' || code || ''' AS column' || n, ',') within group (order by code) ||
'))'
)
gives:
<?xml version="1.0"?>
<ROWSET>
<ROW>
<COLUMN1>A</COLUMN1>
<COLUMN2>B</COLUMN2>
<COLUMN3>C</COLUMN3>
<COLUMN4>D</COLUMN4>
</ROW>
</ROWSET>
from (select code, rownum n from mapping)

Answer 2

Check Below Query.
select listagg(CODE,' ') within group(order by CODE) CODE
from tableName
Check This Demo.

Answer 3

Use PIVOT:
SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE mapping ( code ) AS
SELECT 'A' FROM DUAL UNION ALL
SELECT 'B' FROM DUAL UNION ALL
SELECT 'C' FROM DUAL UNION ALL
SELECT 'D' FROM DUAL;
Query 1:
SELECT *
FROM (
SELECT ROW_NUMBER() OVER ( ORDER BY code ) rn,
code
FROM mapping
)
PIVOT ( MAX( code ) FOR rn IN (
1 AS column1,
2 AS column2,
3 AS column3,
4 AS coumn4
) )
Results:
| COLUMN1 | COLUMN2 | COLUMN3 | COUMN4 |
|---------|---------|---------|--------|
| A | B | C | D |