Oracle PL/SQL Interview Questions and Answers

What are the cursor attributes used in PL/SQL?

% ISOPEN – Used to check whether a cursor is open or not.
% ROWCOUNT – Used to check the number of rows fetched/updated/deleted.
% FOUND – Used to check whether cursor has fetched any row. True if rows are fetched.
% NOT FOUND – Used to check whether cursor has fetched any row. True if no rows are fetched.

What are % TYPE and % ROWTYPE? What are the advantages of using these over datatypes?

% TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are:
I. Need not know about variable’s data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.

What are the datatypes a available in PL/SQL?
Some scalar data types such as NUMBER, VARCHAR2, DATE, CHAR, LONG, BOOLEAN. Some composite data types such as RECORD & TABLE.
What are the components of a PL/SQL Block?

Declarative part
Executable part
Exception part

What is a stored procedure ?
A stored procedure is a sequence of statements that perform specific task. A stored procedure is a named pl/sql block which performs an action.It is stored in the database as a schema object and can be repeatedly executed.It can be invoked, parameterised and nested.
What is a cursor ? Why Cursor is required?
Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
What are advantages of Stored Procedures?

Extensibility,Modularity, Reusability, Maintainability and one time compilation.

How can a function retun more than one value in oracle with proper example?
Basically as per property of function it has to return one value. So the other values can be returned from the out parameter of the function. But its advised if you want more that one return value go for procedure however function will also yield the same result.
What is a cursor for loop ?

Cursor for loop implicitly declares %ROWTYPE as loop index,opens a cursor, fetches rows of values from active set into fields in the record and closes when all the records have been processed.
eg. 

FOR emp_rec IN C1 LOOP
salary_total := salary_total +emp_rec sal;
END LOOP;
Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger? Why?
It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing. yes WE can use COMMIT and ROLLBACK triggers, but by using PRAGAMA AUTONAMOUS_TRANSATIONS. Now the transation treated as a autonomous tansation.
What is a database trigger ? Name some usages of database trigger ?

Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.

Unlike the stored procedure and functions, which have to be called explicitly, the database triggers are fires (executed) or called implicitly whenever the table is affected by any of the above said DML operations.

Till oracle 7.0 only 12 triggers could be associated with a given table, but in higher versions of Oracle there is no such limitation. 

A database trigger has three parts
1. A triggering event
2. A trigger constraint (Optional)
3. Trigger action

A triggering event can be an insert, update, or delete statement or a instance shutdown or startup etc. The trigger fires automatically when any of these events occur.
A trigger constraint specifies a Boolean expression that must be true for the trigger to fire. This condition is specified using the WHEN clause. 
The trigger action is a procedure that contains the code to be executed when the trigger fires.

What is Savepoint?
Savepoint is a point within a particular transaction to which you may rollback without rolling back the entire transaction.

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Who appoints the Chairman and the Members of the Union Public Service Commission?

General Knowledge of World

Which country will host the 2022 Football World Cup?

Area

The angles of a triangle are in the ratio 2 : 4 : 3. The smallest angle of the triangle is?

Which one of the following triples does not represent the sides of a triangle?

If the perimeter of a rectangle is 10 cm and the area is 4 cm2, then its length is?

Height and Distance

An aeroplane flying at a height of 300 m above the ground passes vertically above another plane at an instant when the angles of elevation of the two planes from the same point on the ground are 60º and 45º respectively. What is the height of the lower plane from the ground?

From the top of a building 90 m high, the angles of depression of the top and the bottom of a tree are 30º and 45º respectively. What is the height of the tree?

Trigonometry

What is the value of sinx √( 1 /1+cosx + 1 /1-cosx ) ?

What is cos4 A - sin4 A / cos2 A - sin2 A equal to?

If 7sin2 x +3cos2 x = 4, 0 < x < 90º ,then what is the value of tan x?

If x = a cosθ + b sinθ and y = a sinθ - b cosθ then what is x2 + y2 equal to?

Average

The mean of 5 numbers is 15. If one more number is included, the mean of the 6 numbers becomes 17. What is the included number?

The mean marks obtained by 300 students in a subject are 60. The mean of top 100 students was found to be 80 and the mean of last 100 students was found to be 50. The mean marks of the remaining 100 students are?

In an asymmetrical distribution, of the mean and median of the distribution are 270 and 220 respectively, then the mode of the data is?

Let a, b, c, d, e, f, g be consecutive even numbers and j, k, l, m, n be consecutive odd numbers. What is the average of all the numbers?

Alligation or Mixture

25 kg of alloy X is mixed with 125 kg of alloy Y. If the amount of lead and tin in the alloy X is the ratio 1 : 2 and the amount of lead and tin in the alloy Y is in the ratio 2 : 3, then what is the ratio of lead to tin in the mixture?

Simplification

The ratio of two numbers is 1 : 5 and their product is 320. What is the difference between the square of these two numbers?