单项选择题
A.It must have the UNIQUE attribute.
B.It cannot be created explicitly by the user.
C.It must have the UNIQUE and CLUSTER attributes.
D.It must have the UNIQUE WHERE NOT NULL attribute.
单项选择题 A view is created with the following statement:CREATE VIEW v1 AS SELECT col1, col2, col3, col4 FROM t1 WHERE col4 > 1000 WITH CHECK OPTIONWhat is the effect of the CHECK OPTION clause?（）
单项选择题 Which of the following are all valid DB2 data types?（）
单项选择题 What type of constraint can be used to ensure that, in any given row in a table, the value of one column never exceeds the value of another column?（）