Tag: databases

Quizzes (243) Questions (4862)

Questions Related to databases

Multiple choice technology databases

Examine the structure of the EMPLOYEES and NEW EMPLOYEES tables: EMPLOYEES EMPLOYEE_ID NUMBER Primary Key FIRST_NAME VARCHAR2(25) LAST_NAME VARCHAR2(25) HIRE_DATE DATE NEW EMPLOYEES EMPLOYEE_ID NUMBER Primary Key NAME VARCHAR2(60) Which MERGE statement is valid?

  1. MERGE INTO new_employees c USING employees e ON (c.employee_id = e.employee_id) WHEN MATCHED THEN UPDATE SET c.name = e.first_name ||','|| e.last_name WHEN NOT MATCHED THEN INSERT VALUES(e.employee_id, e.first_name ||', '||e.last_name);

  2. MERGE new_employees c USING employees e ON (c.employee_id = e.employee_id) WHEN EXISTS THEN UPDATE SET c.name = e.first_name ||','|| e.last_name WHEN NOT MATCHED THEN INSERT VALUES(e.employee_id, e.first_name ||', '||e.last_name);

  3. MERGE INTO new employees c USING employees e ON (c.employee_id = e.employee_id) WHEN EXISTS THEN UPDATE SET c.name = e.first_name ||','|| e.last_name WHEN NOT MATCHES THEN INSERT VALUES(e.employee_id, e.first_name ||', '||e.last_name);

  4. MERGE new_employees c FROM employees e ON (c.employee_id = e.employee_id) WHEN MATCHED THEN UPDATE SET c.name = e.first_name ||','|| e.last_name WHEN NOT MATCHED THEN INSERT INTO new_employees VALUES(e.employee_id, e.first_name ||'.'||e.last_name);
Reveal answer Fill a bubble to check yourself
A Correct answer
Full explanation
Multiple choice technology databases

Which of the following is applicable for Exadata Hybrid Columnar Compression?

  1. a. The database stores the same column for a group of rows together

  2. b. The data block does not store the rows in the row-major format

  3. c. The database stores the identical rows together with a reference for each row

  4. d. Database operations works transparently against compressed objects without the need of changing application code
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Full explanation
Multiple choice technology databases

The database stores a set of rows in an internal structure called a compression unit in case of Exadata Hybrid Columnar Compression.

  1. a. Compression unit can span across multiple data blocks

  2. b. The value of particular column can span across multiple blocks

  3. c. If a column in a compression unit is updated, the database will take a lock only on the updated rows

  4. d. If a column in a compression unit is updated, the database will take a lock on the entire compression unit
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Full explanation
Multiple choice technology databases

When tables use Exadata Hybrid Columnar Compression, Oracle DML locks larger blocks of data (compression unit) which might reduce concurrency

  1. a. For basic and online archival compression inserted and updated rows are uncompressed

  2. b. Higher compression levels of Exadata Hybrid Columnar Compression are achieved only with data that is direct-path inserted

  3. c. High CPU overhead in case Warehouse compression

  4. d. Conventional inserts and updates are supported in Exadata Hybrid Columnar Compression but the extent of compression is low
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Full explanation