Returning all dates in dd/mm/yy format from the past 6 months - sql

Question

I am looking to return all days from the past 6 months.
Per example:
Column1
-------
01-OCT-18
30-SEP-18
29-SEP-18
........
01-APR-18
#TimBiegeleisen - Your solution pointed me in the right direction, so you get the points.
#MT0 - "ADD_MONTHS" as far as I know is not used in T-SQL so the the clarification I believe was necessary. but thank you for the pointer with the updates will refrain from doing that in the future.

Answer 1

We can compare each date in Column1 against SYSDATE, 6 months earlier, and then display the dates in the format you want using TO_CHAR with an appropriate format mask:
SELECT
TO_CHAR(Column1, 'dd/mm/yy') AS output
FROM yourTable
WHERE
Column1 >= ADD_MONTHS(SYSDATE, -6);
Demo

Answer 2

This will get you all the dates (in the format in your example) from the last 6 months:
SQL Fiddle
Query 1:
SELECT TO_CHAR( SYSDATE - LEVEL + 1, 'DD-MON-RR' ) AS Column1
FROM DUAL
CONNECT BY SYSDATE - LEVEL + 1 >= ADD_MONTHS( SYSDATE, -6 )
Results:
| COLUMN1 |
|-----------|
| 11-OCT-18 |
| 10-OCT-18 |
| 09-OCT-18 |
...
| 13-APR-18 |
| 12-APR-18 |
| 11-APR-18 |
Update
the idea is to produce a list of days from the past 6 months and a count of how many times a particular value has been recorded against each date
SQL Fiddle
Oracle 11g R2 Schema Setup:
Create an example table with multiple rows for various days:
CREATE TABLE table_name ( value ) AS
SELECT TRUNC( SYSDATE ) - 0 FROM DUAL CONNECT BY LEVEL <= 5
UNION ALL SELECT TRUNC( SYSDATE ) - 1 FROM DUAL CONNECT BY LEVEL <= 3
UNION ALL SELECT TRUNC( SYSDATE ) - 2 FROM DUAL CONNECT BY LEVEL <= 7
UNION ALL SELECT TRUNC( SYSDATE ) - 3 FROM DUAL CONNECT BY LEVEL <= 2
UNION ALL SELECT TRUNC( SYSDATE ) - 4 FROM DUAL CONNECT BY LEVEL <= 1
Query 1:
SELECT TO_CHAR( c.Column1, 'DD-MON-RR' ) AS Column1,
COUNT( t.value ) AS num_values_per_day
FROM (
SELECT TRUNC( SYSDATE ) - LEVEL + 1 AS Column1
FROM DUAL
CONNECT BY TRUNC( SYSDATE ) - LEVEL + 1 >= ADD_MONTHS( SYSDATE, -6 )
) c
LEFT OUTER JOIN table_name t
ON ( c.column1 = t.value )
GROUP BY c.Column1
ORDER BY c.Column1 DESC
Results:
| COLUMN1 | NUM_VALUES_PER_DAY |
|-----------|--------------------|
| 11-OCT-18 | 5 |
| 10-OCT-18 | 3 |
| 09-OCT-18 | 7 |
| 08-OCT-18 | 2 |
| 07-OCT-18 | 1 |
| 06-OCT-18 | 0 |
| 05-OCT-18 | 0 |
...
| 14-APR-18 | 0 |
| 13-APR-18 | 0 |
| 12-APR-18 | 0 |

Answer 3

So for the additional task provided in your comment you might want to adjust Tim Biegeleisens solution a little bit:
SELECT TRUNC(Column1) AS "Day"
, count(*) as "Count"
FROM yourTable
GROUP BY TRUNC(Column1)
WHERE Column1 >= ADD_MONTHS(SYSDATE, -6);

Answer 4

I will add more to it however this was the starting point I needed, I was over complicating the query by trying to use "CONNECT BY LEVEL" the query I had before worked fine for dates in the future but would not return anything previous to the sysdate (I will play around a bit more with the above to figure out how it works but for the time being I know enough).
Thanks for the answer, I was able to figure out the solution for what I wanted via the following:
SELECT col1
FROM table1
WHERE col1 >= add_months(sysdate,-6)