我该怎么办 orderBy 仅当 current date 在/之间 starts_at 以及 ends_at 日期？
例如：

// Suppose Current Date: 2018-10-05

- Example A
  = Starts At: NULL,       Ends At: NULL,       Created At: 2018-10-05
- Example B
  = Starts At: NULL,       Ends At: NULL,       Created At: 2018-10-04
- Example C
  = Starts At: 2018-10-01, Ends At: 2018-10-03, Created At: 2018-10-03
- Example D
  = Starts At: 2018-10-03, Ends At: 2018-10-05, Created At: 2018-10-02
- Example E
  = Starts At: 2018-10-05, Ends At: 2018-10-07, Created At: 2018-10-01
- Example F
  = Starts At: 2018-10-07, Ends At: 2018-10-09, Created At: 2018-09-30

我当前的查询是（列是 starts_at 以及 ends_at ):

Example::orderByRaw('if(isnull(starts_at) >= curdate() and isnull(ends_at) <= curdate(), starts_at, created_at) desc');

导致：

- Example A
- Example B
- Example C
- Example D
- Example E
- Example F

预期结果：

- Example E // First because of starts at 2018-10-05 until 2018-10-07
- Example A --
- Example B   |_ // Same order based expired/null
- Example C   |
- Example D --
- Example F // Still last because starts at is in the future

这是我的小提琴。