单项选择题
Which constraint can be defines only at the column level?（）
A.UNIQUE B.NOT NULL C.CHECK D.PRIMARY KEY E.FOREIGN KEY
单项选择题 In which scenario would TOP N analysis be the best solution?（）
多项选择题 Which three are true regarding the use of outer joins? （）
单项选择题 What is necessary for your query on an existing view to execute successfully?（）
