pivot does not work when using a nested select in SQL - sql

Question

I have a requirement to pivot the columns of a particular table specified from a user.
the problem is the number of columns from each table to pivot is dynamic.
so the code below gets the name of the columns from the table.
SELECT DISTINCT
LISTAGG('''' || column_name || '''', ',')
WITHIN GROUP (ORDER BY column_name) AS temp_in_statement
FROM (SELECT DISTINCT column_name FROM all_tab_columns WHERE table_name = 'DIM_XYZ')
the code above returns the columns in the following format:
col1, col2
I have to use a pivot for this requirement and plug the code above in the code below in order to pivot the columns.
SELECT * FROM
(
SELECT table_name, column_name
FROM ALL_TAB_COLUMNS
WHERE
table_name = 'DIM_XYZ'
)
PIVOT
(
MIN(column_name)
FOR column_name IN (
-- values added manually
'col1','col2'
-- values added manually
)
)
ORDER BY table_name;
The code works fine in this case but when replacing 'col1','col2' by the select statement to retrieve columns names the system throws the following error:
ORA-00936: missing expression
00936. 00000 - "missing expression"
*Cause:
*Action:
Error at Line: 39 Column: 40
CODE:
SELECT * FROM
(
SELECT table_name, column_name
FROM ALL_TAB_COLUMNS
WHERE
table_name = 'DIM_XYZ'
)
PIVOT
(
MIN(column_name)
FOR column_name IN (
--code below does not work when plugged in the statement above
SELECT DISTINCT
LISTAGG('''' || column_name || '''', ',')
WITHIN GROUP (ORDER BY column_name) AS temp_in_statement
FROM (SELECT DISTINCT column_name FROM all_tab_columns WHERE table_name = 'DIM_XYZ')
--code above does not work
)
)
ORDER BY table_name;
----------------
do you guys have any idea how to solve this problem?

Answer 1

You cannot directly add dynamic expressions as an input to Pivot table,
You can try something like this where we retrieve all the columns of the table in a variable via a PL/SQL Block and then pass it in a way to the expected by the Oracle Pivot Table Functionality.
SET serveroutput ON;
DECLARE
sqlquery VARCHAR(32767);
cols VARCHAR2(32767);
BEGIN
SELECT listagg('''' || column_name || '''', ',') within
GROUP(
ORDER BY column_name)
INTO cols
FROM
(SELECT DISTINCT column_name
FROM all_tab_columns
WHERE TABLE_NAME = 'TABLE_NAME')
;
sqlquery := '
SELECT * FROM
(
SELECT table_name, column_name
FROM ALL_TAB_COLUMNS
WHERE
table_name = ''TABLE_NAME''
)
PIVOT
(
MIN(column_name)
FOR column_name IN (
''||cols||''
)
)
ORDER BY table_name';
DBMS_OUTPUT.PUT_LINE(sqlquery);
EXECUTE IMMEDIATE sqlquery;
END;
/