sdc文件格式怎么得到的？请各位大侠多多指教。

You have to manually write initial SDC by yourself following the format. Then you can read into tools and wirte it out.
Usually if there should not be setup and hold violation at same path. You have to check the constraint, clock skew/latency to find out the reason.

为什么在同一条path上不会同时存在setup and hold的violation?
为什么说setup and transition是在同一区的，或者说相关的?

1）你给个"setup和hold在同一条path"的例子
2）什么叫“在同一区的”?

你是做PandR吧?
sdc可以在逻辑综合后由逻辑综合工具写出，如design compiler。
dc_shell> write_sdc ...