A SAS data set is exactly equivalent to the concept of a table (formally, a. âtupleâ) in the relational model. The programmer could use either data step MERGE or use a join. in PROC SQL. Which one to use can be a matter of personal preference. But if you learn each. method well, you can choose the best tool for each specific situation.
An eye twitch is an involuntary spasm of the muscles in the eyelid. Blepharospasm is the medical term for eyelid twitching. Eyelid twitching usually occurs every few seconds and lasts for a few minutes. It may come and go over a period of days or weeks. Sometimes the twitching results in the eye being held closed until the movement stops, but this is not always the case.
In its most common form, eye twitching is harmless and stops on its own, although it may recur occasionally. Sometimes, eye twitching may be the earliest sign of a chronic movement disorder, especially if other facial spasms develop in addition to the eye twitching. Usually, however, there is no identifiable cause. Some of the causes of eyelid spasms that have been identified include: 1  Alcohol intake. 2  Bright lights.