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ORACLE Interview Questions and Answers
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(Continued from previous part...)
GENERAL INTERVIEW QUESTIONS (3)
31.Can null keys be entered in cluster index, normal index ?
Yes.
32.Can Check constraint be used for self referential integrity ? How ?
Yes. In the CHECK condition for a column of a table, we can reference some other column of the same table and thus enforce self referential integrity.
33.What are the min. extents allocated to a rollback extent ?
Two
34.What are the states of a rollback segment ? What is the difference between partly available and needs recovery ?
The various states of a rollback segment are :
ONLINE, OFFLINE, PARTLY AVAILABLE, NEEDS RECOVERY and INVALID.
35.What is the difference between unique key and primary key ?
Unique key can be null; Primary key cannot be null.
36.An insert statement followed by a create table statement followed by rollback ? Will the rows be inserted ?
No.
37.Can you define multiple savepoints ?
Yes.
38.Can you Rollback to any savepoint ?
Yes.
40.What is the maximum no. of columns a table can have ?
254.
41.What is the significance of the & and && operators in PL SQL ?
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.
If a transaction is very large, and the rollback segment is not able to hold the rollback information, then will the transaction span across different rollback segments or will it terminate ?
It will terminate (Please check ).
42.Can you pass a parameter to a cursor ?
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;
43.What are the various types of RollBack Segments ?
Public Available to all instances
Private Available to specific instance
(Continued on next part...)
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