单项选择题
A.COL1 will accept NULL values and can be referenced in another table's foreign key specification.
B.COL1 will not accept NULL values and cannot be referenced in another tables foreign key specification.
C.COL1 will not accept NULL values and can be referenced in another tables foreign key specification.
D.COL1 will accept NULL values and cannot be referenced in another tables foreign key specification.
单项选择题 A DBA has been asked to create a table which will contain a substantial amount of detailed sales information for each calendar month and maintain it to contain only the last 12 months. Which of the following methods will facilitate the online removal of the oldest month’s data?（）
单项选择题 Which of the following is true of an index used to support a UNIQUE constraint?（）
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?（）