Oracle Interview Questions And Answers Set - 12
Questions And Answers Set - 12
How does one use SQL*Loader to load images, sound clips and documents? (for DBA)
SQL*Loader can load data from a "primary data file", SDF (Secondary Data file - for loading nested tables and VARRAYs) or LOGFILE. The LOBFILE method provides and easy way to load documents, images and audio clips into BLOB and CLOB columns. Look at this example:
Given the following table:
CREATE TABLE image_table (
INTO TABLE image_table
FIELDS TERMINATED BY ','
image_data LOBFILE (file_name) TERMINATED BY EOF
What is the difference between the conventional and direct path loader? (for DBA)
The conventional path loader essentially loads the data by using standard INSERT statements. The direct path loader (DIRECT=TRUE) bypasses much of the logic involved with that, and loads directly into the Oracle data files. More information about the restrictions of direct path loading can be obtained from the Utilities Users Guide.
GENERAL INTERVIEW QUESTIONS
What are the various types of Exceptions ?
User defined and Predefined Exceptions.
Can we define exceptions twice in same block ?
What is the difference between a procedure and a function ?
Functions return a single variable by value whereas procedures do not return any variable by value. Rather they return multiple variables by passing variables by reference through their OUT parameter.
Can you have two functions with the same name in a PL/SQL block ?
Can you have two stored functions with the same name ?
Can you call a stored function in the constraint of a table ?
What are the various types of parameter modes in a procedure ?
IN, OUT AND INOUT.
What is Over Loading and what are its restrictions ?
OverLoading means an object performing different functions depending upon the no. of parameters or the data type of the parameters passed to it.
Can functions be overloaded ?
Can 2 functions have same name & input parameters but differ only by return datatype ?
What are the constructs of a procedure, function or a package ?
The constructs of a procedure, function or a package are :
variables and constants
Why Create or Replace and not Drop and recreate procedures ?
So that Grants are not dropped.
Can you pass parameters in packages ? How ?
Yes. You can pass parameters to procedures or functions in a package.
What are the parts of a database trigger ?
The parts of a trigger are:
A triggering event or statement
A trigger restriction
A trigger action
What are the various types of database triggers ?
There are 12 types of triggers, they are combination of :
Insert, Delete and Update Triggers.
Before and After Triggers.
Row and Statement Triggers.
What is the advantage of a stored procedure over a database trigger ?
We have control over the firing of a stored procedure but we have no control over the firing of a trigger.
What is the maximum no. of statements that can be specified in a trigger statement ?
Can views be specified in a trigger statement ?
What are the values of :new and :old in Insert/Delete/Update Triggers ?
INSERT : new = new value, old = NULL
DELETE : new = NULL, old = old value
UPDATE : new = new value, old = old value
What are cascading triggers? What is the maximum no of cascading triggers at a time?
When a statement in a trigger body causes another trigger to be fired, the triggers are said to be cascading. Max = 32.
What are mutating triggers ?
A trigger giving a SELECT on the table on which the trigger is written.
What are constraining triggers ?
A trigger giving an Insert/Update on a table having referential integrity constraint on the triggering table.
Describe Oracle database's physical and logical structure ?
Physical : Data files, Redo Log files, Control file.
Logical : Tables, Views, Tablespaces, etc.
Can you increase the size of a tablespace ? How ?
Yes, by adding datafiles to it.
What is the use of Control files ?
Contains pointers to locations of various data files, redo log files, etc.
What is the use of Data Dictionary ?
Used by Oracle to store information about various physical and logical Oracle structures e.g. Tables, Tablespaces, datafiles, etc
What are the advantages of clusters ?
Access time reduced for joins.
What are the disadvantages of clusters ?
The time for Insert increases.
Can Long/Long RAW be clustered ?
Can null keys be entered in cluster index, normal index ?
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.
What are the min. extents allocated to a rollback extent ?
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.
What is the difference between unique key and primary key ?
Unique key can be null; Primary key cannot be null.
An insert statement followed by a create table statement followed by rollback ? Will the rows be inserted ?
an you define multiple savepoints ?
Can you Rollback to any savepoint ?
What is the maximum no. of columns a table can have ?
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 ).
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;
What are the various types of RollBack Segments ?
Public Available to all instances
Private Available to specific instance
Can you use %RowCount as a parameter to a cursor ?
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))
Is the assignment given below allowed :
ABC = PQR (Where ABC and PQR are records)
Is this for loop allowed :
For x in &Start..&End Loop
How many rows will the following SQL return :
Select * from emp Where rownum < 10;
How many rows will the following SQL return :
Select * from emp Where rownum = 10;
Which symbol preceeds the path to the table in the remote database ?
Are views automatically updated when base tables are updated ?
Can a trigger written for a view ?
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 ?
A table has the following data : [[5, Null, 10]]. What will the average function return ?
Is Sysdate a system variable or a system function?
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 ?
Definition of relational DataBase by Dr. Codd (IBM)?
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.
What is Multi Threaded Server (MTA) ?
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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