PLSQl Interview Questions Part 3

  1. What are the min.extents allocated to a rollback extent ?
Answer: Two
  1. What are the states of a rollback segment ? What is the difference between partly available and needs recovery ?
Answer: The various states of a rollback segment are :
    • ONLINE
    • OFFLINE
    • PARTLY AVAILABLE
    • NEEDS RECOVERY
    • INVALID.
  1. What is the difference between unique key and primary key ?
Answer: Unique key can be null; Primary key cannot be null.
  1. An insert statement followed by a create table statement followed by rollback ? Will the rows be inserted ?
Answer: No.
  1. Can you define multiple savepoints ?
Answer: Yes.
  1. Can you Rollback to any savepoint ?
Answer: Yes.
  1. What is the maximum no.of columns a table can have ?
Answer: 254.
  1. What is the significance of the & and && operators in PL SQL ?
Answer: The & operator means that the PL SQL block requires user input for a variable.
The && operator means that the value of this
 variable should be the same as inputted by the user previously for this same variable
59. Can you pass a parameter to a cursor ?
Answer: Explicit cursors can take parameters, as the example below shows.A cursor parameter can appear in a query wherever a constant can appear.
CURSOR c1 (median IN NUMBER) IS
SELECT
 job, ename FROM emp WHERE sal > median;
  1. What are the various types of RollBack Segments ?
Answer: The types of Rollback sagments are as follows :
    • Public Available to all instances
    • Private Available to specific instance
  1. Can you use %RowCount as a parameter to a cursor ?
Answer: Yes
  1. Is the query below allowed : 
    Select sal, ename Into x From emp Where ename = 'KING' (Where x is a record of Number(4) and Char(15))
Answer: Yes
  1. Is the assignment given below allowed : 
    ABC = PQR (Where ABC and PQR are records)
Answer: Yes
  1. Is this for loop allowed : 
    For x in &Start..&End Loop
Answer: Yes
  1. How many rows will the following SQL return : 
    Select * from emp Where rownum < 10;
Answer: 9 rows
  1. How many rows will the following SQL return : 
    Select * from emp Where rownum = 10;
Answer: No rows
  1. Which symbol preceeds the path to the table in the remote database ?
Answer: @
  1. Are views automatically updated when base tables are updated ?
Answer: Yes
  1. Can a trigger written for a view ?
Answer: No
  1. If all the values from a cursor have been fetched and another fetch is issued, the output will be : error, last record or first record ?
Answer: Last Record
  1. A table has the following data : [[5, Null, 10]].What will the average function return ?
Answer: 7.5
  1. Is Sysdate a system variable or a system function?
Answer: System Function
  1. Consider a sequence whose currval is 1 and gets incremented by 1 by using the nextval reference we get the next number 2.Suppose at this point we issue an rollback and again issue a nextval.What will the output be ?
Answer: 3
  1. Definition of relational DataBase by Dr.Codd (IBM)?
Answer: A Relational Database is a database where all data visible to the user is organized strictly as tables of data values and where all database operations work on these tables.
  1. What is Multi Threaded Server (MTA) ?

Answer: In a Single Threaded Architecture (or a dedicated server configuration) the database manager creates a separate process for each database user.But in MTA the database manager can assign multiple users (multiple user processes) to a single dispatcher (server process), a controlling process that queues request for work thus reducing the databases memory requirement and resources.

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