单项选择题

Which statement explicitly names a constraint?（）

A. ALTER TABLE student_grades   ADD   FOREIGN KEY (student_id) REFERENCES students(student_id);
B. ALTER TABLE student_grades   ADD CONSTRAINT NAME = student_id_fk   FOREIGN KEY (student_id) REFERENCES students(student_id);
C. ALTER TABLE student_grades   ADD CONSTRAINT student_id_fk   FOREIGN KEY (student_id) REFERENCES students(student_id);
D. ALTER TABLE student grades   ADD NAMED CONSTRAINT student_id_fk   FOREIGN KEY (student_id) REFERENCES students(student_id);
E. ALTER TABLE student grades   ADD NAME student_id_fk   FOREIGN KEY (student_id) REFERENCES students(student_id);

点击查看答案

上一题目录下一题

相关考题

单项选择题

You want to display the titles of books that meet these criteria:
1. Purchased before January 21, 2001
2. Price is less then $500 or greater than $900
You want to sort the results by their data of purchase, starting with the most recently bought book.
Which statement should you use?（）

A.
B.
C.
D.

多项选择题

Which two are true about aggregate functions? （）

A. You can use aggregate functions in any clause of a SELECT statement.
B. You can use aggregate functions only in the column list of the SELECT clause and in the WHERE clause of a SELECT statement.
C. You can mix single row columns with aggregate functions in the column list of a SELECT statement by grouping on the single row columns.
D. You can pass column names, expressions, constants, or functions as parameters to an aggregate function.
E. You can use aggregate functions on a table, only by grouping the whole table as one single group.
F. You cannot group the rows of a table by more than one column while using aggregate functions.

单项选择题

Which /SQL*Plus feature can be used to replace values in the WHERE clause?（）

A. Substitution variables
B. Replacement variables
C. Prompt variables
D. Instead-of variables
E. This feature cannot be implemented through /SQL*Plus