A. array B. object C. database D. relationship
Note: Needless to say, relational operation will produce a relationship.
2. The company has many departments and employees. Each employee can only belong to one department, and a department can have multiple employees. The contact type from employees to departments is _ _ c _ _.
A. many-to-many B. one-to-one C. many-to-one D. one-to-many
Note: Obviously, each employee can only belong to one department, and a department has multiple employees. From employee to department refers to the relationship between these two entities, not the relationship between an employee (specific to a person) and a department (specific to a department).
3. In the SQL language, the _ d _ _ of the database is realized by GRANT/REVOKE statement.
A. Concurrency control B. Integrity control C. Consistency control D. Security control
Explanation: authorization statement, control user rights and ensure security.
4. The description of dynamic incremental backup is _ _ _ d _ _.
The dynamic incremental backup process does not allow external transaction programs to access the database.
B. Dynamic incremental backup will back up all data.
C. After loading the dynamic incremental backup, the database is in a consistent state.
D dynamic incremental backup should be done when the transaction is not busy.
Description: Differential backup during dynamic incremental backup, B error. It is an error to dynamically allow external transactions to access the database. The data will change before and after backup, so the loaded database is in an inconsistent state. C error
5. The result of rollback execution of transaction rollback instruction is _ _ _ _ _. (2)
A. skip to the beginning of the transaction program to continue execution.
B undo any changes made by the transaction to the database.
C. Error in transaction execution
D. jump to the end of the transaction program to continue execution.
Explanation: the ACID of the transaction, rollback rolls back any changes made by the transaction to the database.
8. Log files are used for transaction failure and recovery of _ _ _ _ _. (2)
A. System failure, CPU failure B. System failure, media failure
C. Media failure, CPU failure D. Media failure, intrusion failure
Explanation: hard knowledge
9. In the SQL language, the _ _ a _ _ statement belongs to the "mode DDL" language.
A. create table B. update C. select D. insert
Interpretation: data definition language
10. Concurrent database operations usually cause problems such as modification loss, _ _ b _ _, reading dirty data, etc. ( )
A. Irrecoverable
Explanation: hard knowledge
1 1, relation R(A, b, c, d), code AB, function dependence {AB→C, AB→D, C→D}, and the highest normal form is) _ _ b _ _. ()
a . 1NF b . 2 NFC . 3 nfd . bcnf
Description: ab-> c，c->； d = & gta B- & gt； D, there is transitive dependence, and every non-primary attribute is completely dependent on ab.
12. if transaction t wants to write data a, it should add __A__. () to the upper node of data a.
A.x lock b.s lock C.IS lock D.IX lock
Explanation: Exclusive lock.