Diploma and ability ,which is more important

Please give me the reasons

When you want to get a job, diploma is more important. Because you are totally a stranger for the boss. You need to show your ability through your diploma.
When you want to get a promotion in the company, ability is more important. Because the boss know you well now. He can judge your qualification through your ability.

Diploma is the proof of ability. If you can prove yourself without diploma, then ability is more important. Otherwise, diploma.

Personally, I think ability is more important.

maybe but no diploma means no chance somehow in our country

学历和能力，哪个更重要？ Mightbe both.