Question 1. what is difference between Co-related sub query and nested sub query?
Answer: Co-related sub query is one in which inner query is evaluated only once and from that result outer
query is evaluated.
Nested query is one in which Inner query is evaluated for multiple times for getting one row of that
outer query.
ex. Query used with IN() clause is Co-related query.
Query used with = operator is Nested query
Question 2. How do I write a cron which will run a SQL query and mail the results to a group?
Answer: Use DBMS_JOB for scheduling a cron job and DBMS_MAIL to send the results through email.
Question 3. What operator performs pattern matching
Answer: LIKE operator
Question 4. What is the use of the DROP option in the ALTER TABLE command
Answer: It is used to drop constraints specified on the table.
Question 5. Which date function is used to find the difference between two dates
Answer: MONTHS_BETWEEN
Question 6. What is the advantage of specifying WITH GRANT OPTION in the GRANT command
Answer: The privilege receiver can further grant the privileges he/she has obtained from the owner to any other user.
Question 7. What is the use of CASCADE CONSTRAINTS
Answer: When this clause is used with the DROP command, a parent table can be dropped even when a child table exists.
Question 8. Which function is used to find the largest integer less than or equal to a specific value
Answer: FLOOR
Question 9. What operator tests column for the absence of data
Answer: IS NULL operator
Question 10. What are the steps involved in Database Startup?
Answer: Start an instance, Mount the Database and Open the Database.
Question 11. What are the steps involved in Database Shutdown?
Answer: Close the Database, Dismount the Database and Shutdown the Instance.
Question 12. What is Restricted Mode of Instance Startup?
Answer: An instance can be started in (or later altered to be in) restricted mode so that when the database is open connections are limited only to those whose user accounts have been granted the RESTRICTED SESSION system privilege.
Question 13. What are the different modes of mounting a Database with the Parallel Server?
Answer: Exclusive Mode If the first instance that mounts a database does so in exclusive mode, only that Instance can mount the database.
Parallel Mode If the first instance that mounts a database is started in parallel mode, other instances that are started in parallel mode can also mount the database.
Question 14. What is Full Backup?
Answer: A full backup is an operating system backup of all data files, on-line redo log files and control file that constitute ORACLE database and the parameter.
Question 15. Can Full Backup be performed when the database is open?
Answer: No.
Question 16. What is Partial Backup?
Answer: A Partial Backup is any operating system backup short of a full backup, taken while the database is open or shut down.
Question 17. 144. What is On-line Redo Log?
Answer: The On-line Redo Log is a set of tow or more on-line redo files that record all committed changes made to the database. Whenever a transaction is committed, the corresponding redo entries temporarily stores in redo log buffers of the SGA are written to an on-line redo log file by the background process LGWR. The on-line redo log files are used in cyclical
fashion.
Question 18. What is Mirrored on-line Redo Log?
Answer: A mirrored on-line redo log consists of copies of on-line redo log files physically located on separate disks, changes made to one member of the group are made to all members.
Question 19. What is Archived Redo Log?
Answer: Archived Redo Log consists of Redo Log files that have archived before being reused.
Question 20. What are the advantages of operating a database in ARCHIVELOG mode over operating it in NO ARCHIVELOG mode?
Answer: Complete database recovery from disk failure is possible only in ARCHIVELOG mode. Online database backup is possible
only in ARCHIVELOG mode.
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