Group row values into columns without hardcoding PL SQL - database

Question

I have a table that looks like this:
MONTH
NAME
July
Ally
July
Don
July
Ken
March
Lee
March
Froyo
March
Denise
April
Kram
I want it to look like this:
July
March
April
Ally
Lee
Kram
Don
Froyo
Ken
Denise
Here is a solution I have tried:
SELECT
(SELECT name FROM mytable WHERE month='July') AS July,
(SELECT name FROM mytable WHERE month='March') AS March,
(SELECT name FROM mytable WHERE month='April') AS April
FROM DUAL;
However, I do not want to hardcode the month values like month='July'
Is there any way to do this?

Answer 1

Seems you're trying to construct a query with conditional aggregate, sorting the month-columns in their order within a year such as
SELECT MAX(CASE
WHEN month = 'March' THEN
name
END) AS March,
MAX(CASE
WHEN month = 'April' THEN
name
END) AS April,
MAX(CASE
WHEN month = 'July' THEN
name
END) AS July
FROM (SELECT t.*,
ROW_NUMBER() OVER(PARTITION BY month ORDER BY name) AS rn
FROM t) -- "t" represents your mentioned table
GROUP BY rn
ORDER BY rn
and you can generate a stored function code as you wish to make it dynamic such as
CREATE OR REPLACE FUNCTION Get_People_By_Months RETURN SYS_REFCURSOR IS
v_recordset SYS_REFCURSOR;
v_sql VARCHAR2(32767);
v_cols VARCHAR2(32767);
BEGIN
SELECT LISTAGG('MAX(CASE WHEN month = '''||month||''' THEN name END) AS '||month ,',')
WITHIN GROUP (ORDER BY month_nr)
INTO v_cols
FROM (SELECT DISTINCT t.month, m.month_nr
FROM t
JOIN (SELECT TO_CHAR(TO_DATE(level, 'mm'),
'Month',
'NLS_DATE_LANGUAGE=English') AS month,
level AS month_nr
FROM dual
CONNECT BY level <= 12) m
ON t.month = TRIM(m.month));
v_sql :='SELECT '|| v_cols ||'
FROM (SELECT t.*, ROW_NUMBER() OVER (PARTITION BY month ORDER BY name) AS rn
FROM t)
GROUP BY rn
ORDER BY rn';
OPEN v_recordset FOR v_sql;
DBMS_OUTPUT.PUT_LINE(v_sql);
RETURN v_recordset;
END;
/
then invoke from the SQL Developer's console as
SQL> DECLARE
result SYS_REFCURSOR;
BEGIN
:result := Get_People_By_Months;
END;
/
SQL> PRINT result;