order date for values with unknown day and month - sql

Question

I'm developing a website with events from the past. For some events the whole date is known, for some the month of the year and for some only the year. Table event looks like:
id
content
date -> YYYY-MM-DD (date data type)
year -> true, if only year is known, otherwise false
monthandyear -> true if only year and month is known, otherwise false
I would like to list the contents of the table in the following order:
descending by date
if only the month and year are known (monthandyear is set to
true), the content should be listed as the last of that month
if only the year is known (year is set to true), the content should be listed as the last of that year
What is the best solution to this problem?
I'm using DQL:
SELECT p FROM App:Event p ORDER BY p.date DESC ...

Answer 1

You can use conditional logic. Assuming that date is a string:
order by left(date, 4),
(case when not year and not yearmonth then 1 else 2 end),
left(date, 7),
(case when not yearmonth then 1 else 2 end)
date
Edit:
If date is of type date, then:
order by year(date),
(case when not year and not yearmonth then 1 else 2 end),
month(date),
(case when not yearmonth then 1 else 2 end)
date

Answer 2

I solved the problem using Gordon's answer. In DQL it looks like:
$this->getEntityManager()
->createQuery(
'SELECT '
. 'p, '
. '(CASE WHEN (p.year = :yes) THEN 1 ELSE 2 END) as HIDDEN ORD1, '
. '(CASE WHEN (p.monthandyear = :yes) THEN 1 ELSE 2 END) as HIDDEN ORD2 '
. 'FROM App:Event p '
. 'ORDER BY SUBSTRING(p.dateandtime, 1, 4) DESC, ORD1 DESC, SUBSTRING(p.dateandtime, 1, 7) DESC, ORD2 DESC, p.dateandtime DESC'
)
->setParameters(array("no" => false, "yes" => true))
->getResult();