DELTALAKE AZURE CLOUD DATABRICS -PYSPARK SNOWFLAKE: October 2014

What are the various types of queries ?

Answer: The types of queries are:

Normal Queries

Sub Queries

Co-related queries

Nested queries

Compound queries

What is a transaction ?

Answer: A transaction is a set of SQL statements between any two COMMIT and ROLLBACK statements.

What is implicit cursor and how is it used by Oracle ?

Answer: An implicit cursor is a cursor which is internally created by Oracle.It is created by Oracle for each individual SQL.

Which of the following is not a schema object : Indexes, tables, public synonyms, triggers and packages ?

Answer: Public synonyms

What is PL/SQL?

Answer: PL/SQL is Oracle's Procedural Language extension to SQL.The language includes object oriented programming techniques such as encapsulation, function overloading, information hiding (all but inheritance), and so, brings state-of-the-art programming to the Oracle database server and a variety of Oracle tools.

Is there a PL/SQL Engine in SQL*Plus?

Answer: No.Unlike Oracle Forms, SQL*Plus does not have a PL/SQL engine.Thus, all your PL/SQL are send directly to the database engine for execution.This makes it much more efficient as SQL statements are not stripped off and send to the database individually.

Is there a limit on the size of a PL/SQL block?

Answer: Currently, the maximum parsed/compiled size of a PL/SQL block is 64K and the maximum code size is 100K.You can run the following select statement to query the size of an existing package or procedure. SQL> select * from dba_object_size where name = 'procedure_name'

Can one read/write files from PL/SQL?

Answer: Included in Oracle 7.3 is a UTL_FILE package that can read and write files.The directory you intend writing to has to be in your INIT.ORA file (see UTL_FILE_DIR=...parameter).

Before Oracle 7.3 the only means of writing a file was to use DBMS_OUTPUT with the SQL*Plus SPOOL command.

DECLARE

fileHandler UTL_FILE.FILE_TYPE;

BEGIN

fileHandler := UTL_FILE.FOPEN('/home/oracle/tmp', 'myoutput','W');

UTL_FILE.PUTF(fileHandler, 'Value of func1 is %sn', func1(1));

UTL_FILE.FCLOSE(fileHandler);

END;

Can you use a DDL in a procedure ? How ?

Answer: From PL/SQL V2.1 one can use the DBMS_SQL package to execute dynamic SQL statements.

Eg: CREATE OR REPLACE PROCEDURE DYNSQL AS

cur integer;

rc integer;

BEGIN

cur := DBMS_SQL.OPEN_CURSOR;

DBMS_SQL.PARSE(cur,'CREATE TABLE X (Y DATE)',

DBMS_SQL.NATIVE);

rc := DBMS_SQL.EXECUTE(cur);

DBMS_SQL.CLOSE_CURSOR(cur);

END;

What are the various types of Exceptions ?

Answer: User defined and Predefined Exceptions.

Can we define exceptions twice in same block ?

Answer: No.

What is the difference between a procedure and a function ?

Answer: 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 ?

Answer: Yes.

Can you have two stored functions with the same name ?

Answer: Yes.

Can you call a stored function in the constraint of a table ?

Answer: No.

What are the various types of parameter modes in a procedure ?

Answer: IN, OUT AND INOUT.

What is Over Loading and what are its restrictions ?

Answer: 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 ?

Answer: Yes.

Can 2 functions have same name & input parameters but differ only by return datatype

Answer: No.

What are the constructs of a procedure, function or a package ?

Answer: The constructs of a procedure, function or a package are :

variables and constants

cursors

exceptions

Why Create or Replace and not Drop and recreate procedures ?

Answer: So that Grants are not dropped.

Can you pass parameters in packages ? How ?

Answer: Yes.You can pass parameters to procedures or functions in a package.

What are the parts of a database trigger ?

Answer: 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 ?

Answer: 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 ?

Answer: 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 ?

Answer: One.

Can views be specified in a trigger statement ?

Answer: No

What are the values of :new and :old in Insert/Delete/Update Triggers ?

Answer: 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?

Answer: 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 ?

Answer: A trigger giving a SELECT on the table on which the trigger is written.

What are constraining triggers ?

Answer: A trigger giving an Insert/Updat e on a table having referential integrity constraint on the triggering table.

Describe Oracle database's physical and logical structure ?

Answer:

Physical : Data files, Redo Log files, Control file.

Logical : Tables, Views, Tablespaces, etc.

Can you increase the size of a tablespace ? How ?

Answer: Yes, by adding datafiles to it.

Can you increase the size of datafiles ? How ?

Answer: No (for Oracle 7.0)

Yes (for Oracle 7.3 by using the Resize clause )

What is the use of Control files ?

Answer: Contains pointers to locations of various data files, redo log files, etc.

What is the use of Data Dictionary ?

Answer: It 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 ?

Answer: Access time reduced for joins.

What are the disadvantages of clusters ?

Answer: The time for Insert increases.

Can Long/Long RAW be clustered ?

Answer: No.

Can null keys be entered in cluster index, normal index ?

Answer: Yes.

Can Check constraint be used for self referential integrity ? How ?

Answer: 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 ?

Answer: Two

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.

What is the difference between unique key and primary key ?

Answer: 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 ?

Answer: No.

Can you define multiple savepoints ?

Answer: Yes.

Can you Rollback to any savepoint ?

Answer: Yes.

What is the maximum no.of columns a table can have ?

Answer: 254.

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

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;

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

Can you use %RowCount as a parameter to a cursor ?

Answer: Yes

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

Is the assignment given below allowed :

ABC = PQR (Where ABC and PQR are records)

Answer: Yes

Is this for loop allowed : For x in &Start..&End Loop

Answer: Yes

How many rows will the following SQL return : Select * from emp Where rownum < 10;

Answer: 9 rows

How many rows will the following SQL return : Select * from emp Where rownum = 10;

Answer: No rows

Which symbol preceeds the path to the table in the remote database ?

Answer: @

Are views automatically updated when base tables are updated ?

Answer: Yes

Can a trigger written for a view ?

Answer: No

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

A table has the following data : [[5, Null, 10]].What will the average function return ?

Answer: 7.5

Is Sysdate a system variable or a system function?

Answer: 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 ?

Answer: 3

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.

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.

What is Functional Dependency?

Answer: Given a relation R, attribute Y of R is functionally dependent on attribute X of R if and only if each X-value has associated with it precisely one -Y value in R

What is Auditing ?

Answer: The database has the ability to audit all actions that take place within it. a) Login attempts, b) Object Accesss, c) Database Action Result of Greatest(1,NULL) or Least(1,NULL) NULL

While designing in client/server what are the 2 imp.things to be considered ?

Answer: Network Overhead (traffic), Speed and Load of client server

What are the disadvantages of SQL ?

Answer: Disadvantages of SQL are :

Cannot drop a field

Cannot rename a field

Cannot manage memory

Procedural Language option not provided

Index on view or index on index not provided

View updation problem

When to create indexes ?

Answer: To be created when table is queried for less than 2% or 4% to 25% of the table rows.

How can you avoid indexes ?

Answer: To make index access path unavailable Use FULL hint to optimizer for full table scan Use INDEX or AND-EQUAL hint to optimizer to use one index or set to indexes instead of another. Use an expression in the Where Clause of the SQL.

What is the result of the following SQL : Select 1 from dual UNION Select 'A' from dual;

Answer: Error

Can database trigger written on synonym of a table and if it can be then what would be the effect if original table is accessed.

Answer: Yes, database trigger would fire.

Can you alter synonym of view or view ?

Answer: No

Can you create index on view

Answer: No.

What is the difference between a view and a synonym ?

Answer: Synonym is just a second name of table used for multiple link of database.View can be created with many tables, and with virtual columns and with conditions.But synonym can be on view.

What's the length of SQL integer ?

Answer: 32 bit length

What is the difference between foreign key and reference key ?

Answer: Foreign key is the key i.e.attribute which refers to another table primary key. Reference key is the primary key of table referred by another table.

Can dual table be deleted, dropped or altered or updated or inserted ?

Answer: Yes

If content of dual is updated to some value computation takes place or not ?

Answer: Yes

If any other table same as dual is created would it act similar to dual?

Answer: Yes

For which relational operators in where clause, index is not used ?

Answer: <> , like '%...' is NOT functions, field +constant, field||''

Assume that there are multiple databases running on one machine.How can you switch from one to another ?

Answer: Changing the ORACLE_SID

What are the advantages of Oracle ?

Answer: Portability : Oracle is ported to more platforms than any of its competitors, running on more than 100 hardware platforms and 20 networking protocols. Market Presence : Oracle is by far the largest RDBMS vendor and spends more on R & D than most of its competitors earn in total revenue.This market clout means that you are unlikely to be left in the lurch by Oracle and there are always lots of third party interfaces available. Backup and Recovery : Oracle provides industrial strength support for on-line backup and recovery and good software fault tolerence to disk failure.You can also do point-in-time recovery. Performance : Speed of a 'tuned' Oracle Database and application is quite good, even with large databases.Oracle can manage > 100GB databases. Multiple database support : Oracle has a superior ability to manage multiple databases within the same transaction using a two-phase commit protocol.

What is a forward declaration ? What is its use ?

Answer: PL/SQL requires that you declare an identifier before using it.Therefore, you must declare a subprogram before calling it.This declaration at the start of a subprogram is called forward declaration.A forward declaration consists of a subprogram specification terminated by a semicolon.

What are actual and formal parameters ?

Answer: Actual Parameters : Subprograms pass information using parameters.The variables or expressions referenced in the parameter list of a subprogram call are actual parameters.For example, the following procedure call lists two actual parameters named emp_num and amount:

Eg.raise_salary(emp_num, amount);Formal Parameters : The variables declared in a subprogram specification and referenced in the subprogram body are formal parameters.For example, the following procedure declares two formal parameters named emp_id and increase:

Eg.PROCEDURE raise_salary (emp_id INTEGER, increase REAL) IS current_salary REAL;

What are the types of Notation ?

Answer: Position, Named, Mixed and Restrictions.

What all important parameters of the init.ora are supposed to be increased if you want to increase the SGA size ?

Answer: In our case, db_block_buffers was changed from 60 to 1000 (std values are 60, 550 & 3500) shared_pool_size was changed from 3.5MB to 9MB (std values are 3.5, 5 & 9MB) open_cursors was changed from 200 to 300 (std values are 200 & 300) db_block_size was changed from 2048 (2K) to 4096 (4K) {at the time of database creation}. The initial SGA was around 4MB when the server RAM was 32MB and The new SGA was around 13MB when the server RAM was increased to 128MB.

1. What is PL/SQL ?

PL/SQL is a procedural language which has interactive SQL, as well as procedural programming language constructs like conditional branching and iteration.

2. Differentiate between % ROWTYPE and TYPE RECORD.

% ROWTYPE is used when a query returns an entire row of a table or view.

TYPE RECORD, on the other hand, is used when a query returns column of different tables or views.

Eg. TYPE r_emp is RECORD (sno smp.smpno%type,sname smp sname %type)

e_rec smp ROWTYPE

Cursor c1 is select smpno,dept from smp;

e_rec c1 %ROWTYPE

3. Explain uses of cursor.

Cursor is a named private area in SQL from which information can be accessed. They are required to process each row individually for queries which return multiple rows.

4. Show code of a cursor for loop.

Cursor declares %ROWTYPE as loop index implicitly. It then opens a cursor, gets rows of values from the active set in fields of the record and shuts when all records are processed.

Eg. FOR smp_rec IN C1 LOOP

totalsal=totalsal+smp_recsal;

ENDLOOP;

5. Explain the uses of database trigger.

A PL/SQL program unit associated with a particular database table is called a database trigger. It is used for :

1)Audit data modifications.

2)Log events transparently.

3)Enforce complex business rules.

4)Maintain replica tables

5)Derive column values

6)Implement Complex security authorizations

6. What are the two types of exceptions.

Error handling part of PL/SQL block is called Exception. They have two types : user_defined and predefined.

7. Show some predefined exceptions.

DUP_VAL_ON_INDEX

ZERO_DIVIDE

NO_DATA_FOUND

TOO_MANY_ROWS

CURSOR_ALREADY_OPEN

INVALID_NUMBER

INVALID_CURSOR

PROGRAM_ERROR

TIMEOUT _ON_RESOURCE

STORAGE_ERROR

LOGON_DENIED

VALUE_ERROR

etc.

8. Explain Raise_application_error.

It is a procedure of package DBMS_STANDARD that allows issuing of user_defined error messages from database trigger or stored sub-program.

9.Show how functions and procedures are called in a PL/SQL block.

Function is called as a part of an expression.

total:=calculate_sal(‘b644’)

Procedure is called as a statement in PL/SQL.

calculate_bonus(‘b644’);

10. Explain two virtual tables available at the time of database trigger execution.

Table columns are referred as THEN.column_name and NOW.column_name.

For INSERT related triggers, NOW.column_name values are available only.

For DELETE related triggers, THEN.column_name values are available only.

For UPDATE related triggers, both Table columns are available.

11. What are the rules to be applied to NULLs whilst doing comparisons?

1) NULL is never TRUE or FALSE

2) NULL cannot be equal or unequal to other values

3) If a value in an expression is NULL, then the expression itself evaluates to NULL except for concatenation operator (||)

12. How is a process of PL/SQL compiled?

Compilation process includes syntax check, bind and p-code generation processes.

Syntax checking checks the PL/SQL codes for compilation errors. When all errors are corrected, a storage address is assigned to the variables that hold data. It is called Binding. P-code is a list of instructions for the PL/SQL engine. P-code is stored in the database for named blocks and is used the next time it is executed.

13. Differentiate between Syntax and runtime errors.

A syntax error can be easily detected by a PL/SQL compiler. For eg, incorrect spelling.

A runtime error is handled with the help of exception-handling section in an PL/SQL block. For eg, SELECT INTO statement, which does not return any rows.

14. Explain Commit, Rollback and Savepoint.

For a COMMIT statement, the following is true:

· Other users can see the data changes made by the transaction.

· The locks acquired by the transaction are released.

· The work done by the transaction becomes permanent.

A ROLLBACK statement gets issued when the transaction ends, and the following is true.

· The work done in a transition is undone as if it was never issued.

· All locks acquired by transaction are released.

It undoes all the work done by the user in a transaction. With SAVEPOINT, only part of transaction can be undone.

15. Define Implicit and Explicit Cursors.

A cursor is implicit by default. The user cannot control or process the information in this cursor.

If a query returns multiple rows of data, the program defines an explicit cursor. This allows the application to process each row sequentially as the cursor returns it.

16. Explain mutating table error.

It occurs when a trigger tries to update a row that it is currently using. It is fixed by using views or temporary tables, so database selects one and updates the other.

17. When is a declare statement required?

DECLARE statement is used by PL/SQL anonymous blocks such as with stand alone, non-stored procedures. If it is used, it must come first in a stand alone file.

18. How many triggers can be applied to a table?

A maximum of 12 triggers can be applied to one table.

19. What is the importance of SQLCODE and SQLERRM?

SQLCODE returns the value of the number of error for the last encountered error whereas SQLERRM returns the message for the last error.

20. If a cursor is open, how can we find in a PL/SQL Block?

the %ISOPEN cursor status variable can be used.

21. Show the two PL/SQL cursor exceptions.

Cursor_Already_Open

Invaid_cursor

22. What operators deal with NULL?

NVL converts NULL to another specified value.

var:=NVL(var2,’Hi’);

IS NULL and IS NOT NULL can be used to check specifically to see whether the value of a variable is NULL or not.

23. Does SQL*Plus also have a PL/SQL Engine?

No, SQL*Plus does not have a PL/SQL Engine embedded in it. Thus, all PL/SQL code is sent directly to database engine. It is much more efficient as each statement is not individually stripped off.

24. What packages are available to PL/SQL developers?

DBMS_ series of packages, such as, DBMS_PIPE, DBMS_DDL, DBMS_LOCK, DBMS_ALERT, DBMS_OUTPUT, DBMS_JOB, DBMS_UTILITY, DBMS_SQL, DBMS_TRANSACTION, UTL_FILE.

25. Explain 3 basic parts of a trigger.

· A triggering statement or event.

· A restriction

· An action

1. What is PL/SQL?

PL/SQL is a procedural language that has both interactive SQL and procedural programming language constructs such as iteration, conditional branching.

2. What is the basic structure of PL/SQL?

PL/SQL uses block structure as its basic structure. Anonymous blocks or nested blocks can be used in PL/SQL.

3. What are the components of a PL/SQL block?

A set of related declarations and procedural statements is called block.

4. What are the components of a PL/SQL Block?

Declarative part, Executable part and Execption part.

5. 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.

6. 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.

7. What is difference between % ROWTYPE and TYPE RECORD ?

% ROWTYPE is to be used whenever query returns a entire row of a table or view.

TYPE rec RECORD is to be used whenever query returns columns of different table or views and variables.

E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type );

e_rec emp% ROWTYPE

Cursor c1 is select empno,deptno from emp;

e_rec c1 %ROWTYPE.

8. What is PL/SQL table?

Objects of type TABLE are called "PL/SQL tables", which are modelled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key.

9. 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.

10. Explain the two types of Cursors?

There are two types of cursors, Implict Cursor and Explicit Cursor.

PL/SQL uses Implict Cursors for queries.

User defined cursors are called Explicit Cursors. They can be declared and used.

11. What are the PL/SQL Statements used in cursor processing?

DECLARE CURSOR cursor name, OPEN cursor name, FETCH cursor name INTO <variable list> or Record types, CLOSE cursor name.

12. What are the cursor attributes used in PL/SQL?

%ISOPEN - to check whether cursor is open or not

% ROWCOUNT - number of rows featched/updated/deleted.

% FOUND - to check whether cursor has fetched any row. True if rows are featched.

% NOT FOUND - to check whether cursor has featched any row. True if no rows are featched.

These attributes are proceded with SQL for Implict Cursors and with Cursor name for Explict Cursors.

13. 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;

14. What will happen after commit statement ?

Cursor C1 is

Select empno,

ename from emp;

Begin

open C1; loop

Fetch C1 into

eno.ename;

Exit When

C1 %notfound;-----

commit;

end loop;

end;

The cursor having query as SELECT .... FOR UPDATE gets closed after COMMIT/ROLLBACK.

The cursor having query as SELECT.... does not get closed even after COMMIT/ROLLBACK.

15. Explain the usage of WHERE CURRENT OF clause in cursors ?

WHERE CURRENT OF clause in an UPDATE,DELETE statement refers to the latest row fetched from a cursor.

16. 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 modificateions, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.

17. How many types of database triggers can be specified on a table? What are they?

Insert Update Delete

Before Row o.k. o.k. o.k.

After Row o.k. o.k. o.k.

Before Statement o.k. o.k. o.k.

After Statement o.k. o.k. o.k.

If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.

If WHEN clause is specified, the trigger fires according to the retruned boolean value.

18. 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.

19. What are two virtual tables available during database trigger execution?

The table columns are referred as OLD.column_name and NEW.column_name.

For triggers related to INSERT only NEW.column_name values only available.

For triggers related to UPDATE only OLD.column_name NEW.column_name values only available.

For triggers related to DELETE only OLD.column_name values only available.

20. What happens if a procedure that updates a column of table X is called in a database trigger of the same table?

Mutation of table occurs.

21. Write the order of precedence for validation of a column in a table ?

I. done using Database triggers.

ii. done using Integarity Constraints.

22. What is an Exception? What are types of Exception?

Exception is the error handling part of PL/SQL block. The types are Predefined and user_defined. Some of Predefined execptions are.

CURSOR_ALREADY_OPEN

DUP_VAL_ON_INDEX

NO_DATA_FOUND

TOO_MANY_ROWS

INVALID_CURSOR

INVALID_NUMBER

LOGON_DENIED

NOT_LOGGED_ON

PROGRAM-ERROR

STORAGE_ERROR

TIMEOUT_ON_RESOURCE

VALUE_ERROR

ZERO_DIVIDE

OTHERS.

23. What is Pragma EXECPTION_INIT? Explain the usage?

The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error.

e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number)

24. What is Raise_application_error?

Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue an user_defined error messages from stored sub-program or database trigger.

25. What are the return values of functions SQLCODE and SQLERRM?

SQLCODE returns the latest code of the error that has occured.

SQLERRM returns the relevant error message of the SQLCODE.

26. Where the Pre_defined_exceptions are stored?

In the standard package.

Procedures, Functions & Packages;

27. What is a stored procedure?

A stored procedure is a sequence of statements that perform specific function.

30. What is difference between a PROCEDURE & FUNCTION?

A FUNCTION is alway returns a value using the return statement.

A PROCEDURE may return one or more values through parameters or may not return at all.

31. What are advantages of Stored Procedures?

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

32. What are the modes of parameters that can be passed to a procedure?

IN,OUT,IN-OUT parameters.

33. What are the two parts of a procedure?

Procedure Specification and Procedure Body.

34. Give the structure of the procedure?

PROCEDURE name (parameter list.....)

local variable declarations

BEGIN

Executable statements.

Exception.

exception handlers

end;

35. Give the structure of the function?

FUNCTION name (argument list .....) Return datatype is

local variable declarations

Begin

executable statements

Exception

execution handlers

End;

36. Explain how procedures and functions are called in a PL/SQL block ?

Function is called as part of an expression.

sal := calculate_sal ('a822');

procedure is called as a PL/SQL statement

calculate_bonus ('A822');

37. What is Overloading of procedures?

The Same procedure name is repeated with parameters of different datatypes and parameters in different positions, varying number of parameters is called overloading of procedures.

e.g. DBMS_OUTPUT put_line

38. What is a package? What are the advantages of packages?

Package is a database object that groups logically related procedures.

The advantages of packages are Modularity, Easier Applicaton Design, and Information.

Hiding,. Reusability and Better Performance.

39. What are two parts of package?

The two parts of package are PACKAGE SPECIFICATION & PACKAGE BODY.

Package Specification contains declarations that are global to the packages and local to the schema.

Package Body contains actual procedures and local declaration of the procedures and cursor declarations.

40. What is difference between a Cursor declared in a procedure and Cursor declared in a package specification?

A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package.

A cursor declared in a procedure is local to the procedure that can not be accessed by other procedures.

41. How packaged procedures and functions are called from the following ?

a. Stored procedure or anonymous block

b. an application program such a PRC *C, PRO* COBOL

c. SQL *PLUS

a. PACKAGE NAME.PROCEDURE NAME (parameters);

variable := PACKAGE NAME.FUNCTION NAME (arguments);

EXEC SQL EXECUTE

BEGIN

PACKAGE NAME.PROCEDURE NAME (parameters)

variable := PACKAGE NAME.FUNCTION NAME (arguments);

END;

END EXEC;

c. EXECUTE PACKAGE NAME.PROCEDURE if the procedures does not have any out/in-out parameters. A function can not be called.

42. Name the tables where characteristics of Package, procedure and functions are stored?

User_objects, User_Source and User_error.

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