Oracle Interview Questions with Answers


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What is use of a cursor variable? How it is defined.

A cursor variable is associated with different statements at run time, which can hold different values at run time. Static cursors can only be associated with one run time query. A cursor variable is reference type(like a pointer in C). Declaring a cursor variable: TYPE type_name IS REF CURSOR RETURN return_type type_name is the name of the reference type,return_type is a record type indicating the types of the select list that will eventually be returned by the cursor variable.

What should be the return type for a cursor variable.Can we use a scalar data type as return type?

The return type for a cursor must be a record type.It can be declared explicitly as a user-defined or %ROWTYPE can be used. eg TYPE t_studentsref IS REF CURSOR RETURN students%ROWTYPE

How you open and close a cursor variable.Why it is required?

OPEN cursor variable FOR SELECT…Statement CLOSE cursor variable In order to associate a cursor variable with a particular SELECT statement OPEN syntax is used.In order to free the resources used for the query CLOSE statement is used.

How you were passing cursor variables in PL/SQL 2.2?

In PL/SQL 2.2 cursor variables cannot be declared in a package.This is because the storage for a cursor variable has to be allocated using Pro*C or OCI with version 2.2,the only means of passing a cursor variable to a PL/SQL block is via bind variable or a procedure parameter. Can cursor variables be stored in PL/SQL tables.If yes how.If not why. No, a cursor variable points a row which cannot be stored in a two-dimensional PL/SQL table.

Difference between procedure and function.

Functions are named PL/SQL blocks that return a value and can be called with arguments procedure a named block that can be called with parameter. A procedure all is a PL/SQL statement by itself, while a Function call is called as part of an expression.

What are different modes of parameters used in functions and procedures.

IN OUT INOUT

What is difference between a formal and an actual parameter?

The variables declared in the procedure and which are passed, as arguments are called actual, the parameters in the procedure declaration. Actual parameters contain the values that are passed to a procedure and receive results. Formal parameters are the placeholders for the values of actual parameters

Can the default values be assigned to actual parameters?

Yes

Can a function take OUT parameters.If not why.

No.A function has to return a value,an OUT parameter cannot return a value.

What is syntax for dropping a procedure and a function .Are these operations possible?

Drop Procedure procedure_name Drop Function function_name

What are ORACLE PRECOMPILERS?

Using ORACLE PRECOMPILERS ,SQL statements and PL/SQL blocks can be contained inside 3GL programs written in C,C++,COBOL,PASCAL, FORTRAN,PL/1 AND ADA. The Precompilers are known as Pro*C,Pro*Cobol,… This form of PL/SQL is known as embedded pl/sql,the language in which pl/sql is embedded is known as the host language. The prcompiler translates the embedded SQL and pl/sql ststements into calls to the precompiler runtime library.The output must be compiled and linked with this library to creater an executable.

What is OCI. What are its uses?

Oracle Call Interface is a method of accesing database from a 3GL program. Uses–No precompiler is required,PL/SQL blocks are executed like other DML statements. The OCI library provides -functions to parse SQL statements -bind input variables -bind output variables -execute statements -fetch the results

Difference between database triggers and form triggers?

a) Data base trigger(DBT) fires when a DML operation is performed on a data base table.Form trigger(FT) Fires when user presses a key or navigates between fields on the screen b) Can be row level or statement level No distinction between row level and statement level. c) Can manipulate data stored in Oracle tables via SQL Can manipulate data in Oracle tables as well as variables in forms. d) Can be fired from any session executing the triggering DML statements. Can be fired only from the form that define the trigger. e) Can cause other database triggers to fire.Can cause other database triggers to fire,but not other form triggers.

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