To enter a night club in Dubai, you are expected to wear decent clothes. Especially men have many restrictions. For men, Smart-casual club wear is recommended. To enter any of the many night clubs in Dubai you should wear shirts with collar, good quality jeans or proper trousers and proper shoes --- no shorts, no sandals, no sports shoes, no ripped jeans, no sports shoes/sneakers
.
For women almost anything goes , except for beach wear
. Also some night clubs only allow couples and single women - but no single men. Some night clubs like the Irish pubs etc are very relaxed as far as dress code for men is concerned.