What's the difference between a primary key and a unique key?
Q: What's the difference between a primary key and a unique key? A: Both primary key and unique enforce uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn't allow NULLs, but unique key allows one NULL only. 비교적 간단하니 영어를..
2008. 5. 9. 11:53