Interview Questions.

Q1. What Is Weak Entity Set?

An entity set won't have sufficient attributes to form a primary key, and its primary key compromises of its partial key and primary key of its discern entity, then it's far stated to be Weak Entity set.

Q2. What Is A Database System?

The database and DBMS software program together is referred to as as Database gadget.

Q3. What Is 1 Nf (everyday Form)?

The area of characteristic ought to encompass handiest atomic (easy, indivisible) values.

Q4. Name Two Utilities That Oracle Provides, Which Are Use For Backup And Recovery.

Along with the RDBMS software, Oracle affords  utilities that you can use to back up and repair the database. These utilities are Export and Import.

The Export utility dumps the definitions and facts for the required part of the database to an operating gadget binary record. The Import application reads the document produced with the aid of an export, recreates the definitions of objects, and inserts the facts.

If Export and Import are used as a method of backing up and recuperating the database, all the modifications made to the database cannot be recovered because the export turned into accomplished. The satisfactory you can do is recover the database to the time whilst the export changed into final finished.

Q5. What Is Relational Calculus?

It is an implemented predicate calculus especially tailor-made for relational databases proposed by using E.F. Codd.

E.G. Of languages based on it are DSL ALPHA, QUEL.

Q6. What Do You Mean By Flat File Database?

It is a database in which there are not any applications or consumer access languages. It has no go-report abilties however is user-pleasant and affords person-interface control.

Q7. What Is Buffer Manager?

It is a software module, that's liable for fetching records from disk garage into fundamental reminiscence and deciding what information to be cache in memory.

Q8. What Is Multivalued Dependency?

Multivalued dependency denoted via X Y targeted on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if  tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 have to additionally exist in r with the subsequent properties

 t3[x] = t4[X] = t1[X] = t2[X]

 t3[Y] = t1[Y] and t4[Y] = t2[Y]

 t3[Z] = t2[Z] and t4[Z] = t1[Z]

where [Z = (R-(X U Y)) ]

Q9. What Is Oracle Block? Can Two Oracle Blocks Have The Same Address?

Oracle "formats" the database files into some of Oracle blocks whilst they may be first created—making it easier for the RDBMS software to manipulate the files and less complicated to study facts into the reminiscence areas.

The block size ought to be a multiple of the running gadget block length. Regardless of the block size, the entire block is not to be had for holding facts; Oracle takes up a few area to control the contents of the block. This block header has a minimal size, however it may grow.

These Oracle blocks are the smallest unit of garage. Increasing the Oracle block size can enhance overall performance, but it need to be performed handiest when the database is first created.

Each Oracle block is numbered sequentially for each database file starting at @Two blocks may have the same block cope with if they may be in different database files.

Q10. What Is Fully Functional Dependency?

It is based on concept of complete purposeful dependency. A useful dependency X Y is full practical dependency if removal of any attribute A from X method that the dependency does now not hold any more.

Q11. Describe The Three Levels Of Data Abstraction?

There are 3 stages of abstraction:

 Physical stage: The lowest level of abstraction describes how statistics are saved.

 Logical degree: The next higher stage of abstraction, describes what records are stored in database and what relationship among those statistics.

 View degree: The maximum stage of abstraction describes simplest a part of whole database.

Q12. Define The "integrity Rules"?

There are two Integrity guidelines.

 Entity Integrity: States that “Primary key can not have NULL cost”.

 Referential Integrity: States that “Foreign Key may be either a NULL fee or should be Primary Key price of other relation.

Q13. What Is Dml Compiler?

It translates DML statements in a query language into low-degree education that the query assessment engine can recognize.

Q14. What Is File Manager?

It is a program module, which manages the allocation of space on disk garage and data shape used to symbolize information saved on a disk.

Q15. What Is Vdl (view Definition Language)?

It specifies person views and their mappings to the conceptual schema.

Q16. What Is Data Independence?

Data independence way that “the utility is unbiased of the garage structure and get entry to strategy of records”. In different words, The potential to alter the schema definition in one stage have to no longer affect the schema definition in the subsequent better degree.

Two sorts of Data Independence:

 Physical Data Independence: Modification in physical stage need to now not affect the logical level.

 Logical Data Independence: Modification in logical degree ought to have an effect on the view degree.

Q17. What Is Set-at-a-time Or Set-oriented?

The High degree or Non-procedural DML can specify and retrieve many statistics in a unmarried DML statement. This retrieve of a record is stated to be Set-at-a-time or Set-orientated.

Q18. What Are The Unary Operations In Relational Algebra?

PROJECTION and SELECTION.

Q19. What Is A Checkpoint And When Does It Occur?

A Checkpoint is like a snapshot of the DBMS state. By taking checkpoints, the DBMS can lessen the quantity of labor to be achieved throughout restart inside the occasion of subsequent crashes.

Q20. What Is Join Dependency And Inclusion Dependency?

Join Dependency:

A Join dependency is generalization of Multivalued dependency.A JD R1, R2, ..., Rn is said to hold over a relation R if R1, R2, R3, ..., Rn is a lossless-join decomposition of R . There is no set of sound and complete inference guidelines for JD.

Inclusion Dependency:

An Inclusion Dependency is a assertion of the shape that a few columns of a relation are contained in other columns. A foreign key constraint is an example of inclusion dependency.

Q21. What Is Rdbms Kernel?

Two vital portions of RDBMS architecture are the kernel, which is the software program, and the statistics dictionary, which consists of the device-level statistics systems utilized by the kernel to manage the database

You might think about an RDBMS as an working machine (or set of subsystems), designed specially for controlling records access; its primary features are storing, retrieving, and securing facts. An RDBMS maintains its personal listing of authorized customers and their related privileges; manages reminiscence caches and paging; controls locking for concurrent resource utilization; dispatches and schedules person requests; and manages space usage inside its table-space systems.

Q22. Advantages Of Dbms?

 Redundancy is controlled.

 Unauthorised get entry to is restricted.

 Providing a couple of user interfaces.

 Enforcing integrity constraints.

 Providing backup and healing.

Q23. What Is A Query?

A question with respect to DBMS pertains to consumer commands which are used to have interaction with a information base. The query language may be categorized into statistics definition language and records manipulation language.

Q24. What Is Extension And Intension?

Extension : It is the wide variety of tuples present in a table at any example. This is time dependent.

Intension : It is a constant cost that gives the name, shape of table and the restrictions laid on it.

Q25. What Are Stand-alone Procedures?

Procedures that are not a part of a package are known as stand-alone due to the fact they independently defined. A properly instance of a stand-alone method is one written in a SQL*Forms software. These kinds of procedures aren't to be had for reference from other Oracle equipment. Another hassle of stand-alone processes is that they're compiled at run time, which slows execution.

Q26. What Is Relational Algebra?

It is procedural query language. It includes a hard and fast of operations that take one or  members of the family as enter and produce a new relation.

Q27. What Is Query Evaluation Engine?

It executes low-degree practise generated by compiler.

Q28. What Is An Oracle Instance?

The Oracle machine techniques, also called Oracle historical past tactics, provide functions for the person approaches—capabilities that might in any other case be performed through the person processes themselves Oracle database-wide machine reminiscence is referred to as the SGA, the system international area or shared international area. The information and manipulate structures in the SGA are shareable, and all the Oracle heritage strategies and consumer processes can use them.

The aggregate of the SGA and the Oracle historical past procedures is called an Oracle example.

Q29. What Is System Catalog Or Catalog Relation? How Is Better Known As?

A RDBMS maintains an outline of all of the data that it carries, information approximately each relation and index that it consists of. This records is saved in a set of members of the family maintained with the aid of the gadget called metadata. It is likewise known as information dictionary.

Q30. What Is Authorization And Integrity Manager?

It is the program module, which checks for the pride of integrity constraint and exams the authority of person to get admission to statistics.

Q31. What Is An Entity Set?

It is a collection of all entities of precise entity type within the database.

Q32. What Are Cursors Give Different Types Of Cursors.

PL/SQL uses cursors for all database facts accesses statements. The language supports the use two kinds of cursors.

 Implicit

 Explicit

Q33. What Is Sdl (garage Definition Language)?

This language is to specify the inner schema. This language may specify the mapping among two schemas.

Q34. What Are The Different Phases Of Transaction?

Different phases are

 Analysis section

 Redo Phase

 Undo section

Q35. What Is Ddl (facts Definition Language)?

A data base schema is specifies through a set of definitions expressed by means of a unique language referred to as DDL.

Q36. What Is Data Model?

A series of conceptual gear for describing records, data relationships data semantics and constraints.

Q37. What Is Bcnf (boyce-codd Normal Form)?

A relation schema R is in BCNF if it's miles in 3NF and satisfies a further constraint that for each FD X A, X need to be a candidate key.

Q38. What Is 4nf?

A relation schema R is stated to be in 4NF if for each Multivalued dependency X Y that holds over R, one of following is genuine

 X is subset or equal to (or) XY = R.

 X is a top notch key.

Q39. What Is Transaction Manager?

It is a application module, which ensures that database, stays in a regular country no matter system disasters and concurrent transaction execution proceeds with out conflicting.

Q40. Are The Resulting Relations Of Product And Join Operation The Same?

No.

PRODUCT: Concatenation of every row in one relation with every row in any other.

JOIN: Concatenation of rows from one relation and associated rows from some other.

Q41. What Is A View? How It Is Related To Data Independence?

A view may be notion of as a digital table, that is, a desk that does not surely exist in its personal proper but is alternatively derived from one or more underlying base table. In other words, there is no stored document that direct represents the view instead a definition of view is saved in statistics dictionary. Growth and restructuring of base tables is not reflected in perspectives. Thus the view can insulate customers from the outcomes of restructuring and growth within the database. Hence accounts for logical data independence.

Q42. What Is A Relation Schema And A Relation?

A relation Schema denoted by means of R(A1, A2, …, An) is made up of the relation name R and the list of attributes Ai that it consists of.

A relation is described as a set of tuples. Let r be the relation which includes set tuples (t1, t2, t3, ..., tn). Each tuple is an ordered list of n-values t=(v1,v2, ..., vn).

Q43. What Is Relationship Set?

The series (or set) of comparable relationships.

Q44. Name The Sub-structures Of A Rdbms?

I/O, Security, Language Processing, Process Control, Storage Management, Logging and Recovery, Distribution Control, Transaction Control, Memory Management, Lock Management.

Q45. What Is "obvious Dbms"?

It is one, which keeps its Physical Structure hidden from person.

Q46. Not Only Rdbms Takes Care Of Locating Data It Also?

Determines an most efficient get right of entry to direction to save or retrieve the records.

Q47. What Is Meant By Query Optimization?

The segment that identifies an efficient execution plan for comparing a query that has the least estimated cost is referred to as question optimization.

Q48. What Is Database?

A database is a logically coherent collection of information with a few inherent that means, representing some factor of actual world and that is designed, built and populated with facts for a selected purpose.

Q49. What Is Functional Dependency?

A Functional dependency is denoted by X Y between two units of attributes X and Y which might be subsets of R specifies a constraint on the possible tuple which could form a relation country r of R. The constraint is for any  tuples t1 and t2 in r if t1[X] = t2[X] then they have got t1[Y] = t2[Y]. This way the fee of X issue of a tuple uniquely determines the price of component Y.

Q50. How Does Tuple-oriented Relational Calculus Differ From Domain-orientated Relational Calculus?

The tuple-orientated calculus makes use of a tuple variables i.E., variable whose best approved values are tuples of that relation. E.G. QUEL

The area-orientated calculus has domain variables i.E., variables that range over the underlying domains in place of over relation. E.G. ILL, DEDUCE.