多项选择题

Which two statements about subqueries are true? （）

A. A subquery should retrieve only one row.
B. A subquery can retrieve zero or more rows.
C. A subquery can be used only in SQL query statements.
D. Subqueries CANNOT be nested by more than two levels.
E. A subquery CANNOT be used in an SQL query statement that uses group functions.
F. When a subquery is used with an inequality comparison operator in the outer SQL statement, the column list in the SELECT clause of the subquery should contain only one column.

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单项选择题Examine these statements: CREATE ROLE registrar GRANT UPDATE ON dtudent_grades TO registrar; GRANT registrar to user1, user2, user3; What does this set of SQL statements do? （）

A. The set of statements contains an error and does not work.
B. It creates a role called REGISTRAR, adds the MODIFY privilege on the STUDENT_GRADES object to the role, and gives the REGISTRAR role to three users.
C. It creates a role called REGISTRAR, adds the UPDATE privilege on the STUDENT_GRADES object to the role, and gives the REGISTRAR role to three users.
D. It creates a role called REGISTRAR, adds the UPDATE privilege on the STUDENT_GRADES object to the role, and creates three users with the role.
E. It creates a role called REGISTRAR, adds the UPDATE privilege on three users, and gives the REGISTRAR role to the STUDENT_GRADES object.
F. It creates a role called STUDENT_GRADES, adds the UPDATE privilege on three users, and gives the UPDATE role to the registrar.

单项选择题Which view should a user query to display the columns associated with the constraints on a table owned by the user? （）

A. USER_CONSTRAINTS
B. USER_OBJECTS
C. ALL_CONSTRAINTS
D. USER_CONS_COLUMNS
E. USER_COLUMNS

单项选择题The user Alice wants to grant all users query privileges on her DEPT table. Which SQL statement accomplishes this? （）

A. GRANT select ON dept TO ALL_ USER;
B. GRANT select ON dept TO ALL;
C. GRANT QUERY ON dept TO ALL_USERS
D. GRANT select ON dept TO PUBLIC;

单项选择题Which constraint can be defined only at the column level? （）

A. UNIQUE
B. NOT NULL
C. CHECK
D. PRIMARY KEY
E. FOREIGN KEY

多项选择题In which two cases would you use an outer join? （）

A. The tables being joined have NOT NULL columns.
B. The tables being joined have only matched data.
C. The columns being joined have NULL values.
D. The tables being joined have only unmatched data.
E. The tables being joined have both matched and unmatched data.
F. Only when the tables have a primary key/foreign key relationship.