to_date()中的格式掩码也必须用单引号引起来.

The format mask in to_date() must be enclosed within single quotes too.

要生成字符串格式的输出，您需要应用具有相同格式掩码的to_char().

To produce the output in string format you need to apply to_char() with the same format mask.

select to_char(to_date('20160101', 'YYYYMMDD') + level - 1, 'YYYYMMDD') as dt
from   dual
connect by level <= 1 + to_date('20160104', 'YYYYMMDD') - to_date('20160101', 'YYYYMMDD')
;


DT     
--------
20160101
20160102
20160103
20160104