I my order by clause I want to do something like

```
select MyDate
from MyTable
order by case when MyDate is null then 1 else 0 end, MyDate

```

how can I write 

```
order by case when MyDate is null then 1 else 0 end, MyDate

```

in Zend
I already tried

```
->order('by case when MyDate is null then 1 else 0 end', 'MyDate')

```

suggestions?