SQL Server 2005 Editions

SQL Server 2005 is available in following four editions. Capabilities and features vary largely in each edition of SQL Server 2005. I have briefly summarize the edition information here. Detailed capabilities of each edition can be found in BOL.

    * Enterprise:
      Provides a relational database to meet the exacting needs of the largest enterprises and busiest online databases. The Enterprise Edition includes high-end business intelligence support and clustering.

    * SQL Server 2005 Standard Edition:
      Meets the needs of medium-sized companies or large departments in larger companies.

    * SQL Server 2005 Workgroup Edition:
      Meets the needs of small- to medium-sized businesses that don’t require the features of Standard Edition.

    * SQL Server 2005 Mobile Edition:
      Formerly called SQL Server CE. It is free, easy-to-use embedded database engine that lets developers build robust Windows Desktop and mobile applications for all Windows platforms including Windows XP, Vista, Pocket PC, and Smartphone.

    * SQL Server 2005 Express Edition:
      A lightweight free edition intended for use by application programmers.

Database Interview Question

What is the Difference between SQL SERVER 2000 and 2005?
These are following difference between SQL SERVER 2000 and 2005.

1. (PG) The most significant change is the .NET integration with SQL SERVER 2005. Stored procedures, user-defined functions, triggers, aggregates, and user-defined types can now be written using your own favorite .NET language (VB.NET, C#, J# etc.). This support was not there in SQL SERVER 2000 where the only language was T-SQL. In SQL 2005, you have support for two languages T-SQL and .NET.
2. (PG) SQL SERVER 2005 has reporting services for reports which is a newly added feature and does not exist for SQL SERVER 2000. It was a separate installation for SQL Server 2000.
3. (PG) SQL SERVER 2005 has introduced two new data types varbinary (max) and XML. If you remember in SQL SERVER 2000, we had image and text data types. Problem with image and text data types is that they assign the same amount of storage irrespective of what the actual data size is. This problem is solved using varbinary (max) which acts depending on amount of data. One more new data type is included XML which enables you to store XML documents and does schema verification. In SQL SERVER 2000, developers used varchar or text data type and all validation had to be done programmatically.
4. (PG) SQL SERVER 2005 can now process direct incoming HTTP request without IIS Web server. In addition, stored procedure invocation is enabled using the SOAP protocol.
   (PG) Asynchronous mechanism is introduced using server events. In Server event model the server posts an event to the SQL Broker service, later the client can come and retrieve the status by querying the broker.
5. For huge databases, SQLSERVER has provided a cool feature called “Data partitioning”. In data partitioning, you break a single database object such as a table or an index into multiple pieces. But for the client application accessing the single database object, “partitioning” is transparent.
6. In SQL SERVER 2000, if you rebuilt clustered indexes even the non-clustered indexes where rebuilt. But in SQL SERVER 2005 building the clustered indexes does not build the non-clustered indexes.
7. Bulk data uploading in SQL SERVER 2000 was done using BCP (Bulk copy program’s) format files. Now in SQL SERVER 2005 bulk, data uploading uses XML file format.
   In SQL SERVER 2000 there were maximum 16 instances, but in 2005 you can have up to 50 instances.
8. SERVER 2005 has support of “Multiple Active Result Sets” also called as “MARS”. In previous versions of SQL SERVER 2000 in one connection, you could only have one result set. Now in one SQL connection, you can query and have multiple results set.
9. In previous versions of SQL SERVER 2000, system catalog was stored in the master database. In SQL SERVER 2005, it’s stored in a resource database which is stored as sys object. You cannot access the sys object directly as in the older version we were accessing the master database.
10. This is one of the hardware benefits which SQL SERVER 2005 has over SQSERVER 2000 – support of hyper threading. WINDOWS 2003 supports hyper threading; SQL SERVER 2005 can take advantage of the feature unlike SQL SERVER 2000 which did not support hyper threading.Note: Hyper threading is a technology developed by INTEL which creates two logical processors on a single physical hardware processor.
11. SMO will be used for SQL Server Management.
12. AMO (Analysis Management Objects) to manage Analysis Services servers, data sources, cubes, dimensions, measures, and data mining models. You can mapm AMO in old SQL SERVER with DSO (Decision Support Objects).
13. Replication is now managed by RMO (Replication Management Objects).Note: SMO, AMO and RMO are all using .NET Framework.
14. SQL SERVER 2005 uses current user execution context to check rights rather than ownership link chain, which was done in SQL SERVER 2000.Note: There is a question on this later see for execution context questions.
15. In previous versions of SQL SERVER the schema and the user name was same, but in current, the schema is separated from the user. Now the user owns schema.Note: There are questions on this, refer “Schema” later.Note: Ok below are some GUI changes.
    Query analyzer is now replaced by query editor.
16. Business Intelligence development studio will be used to create Business intelligence solutions.
17. OSQL and ISQL command line utility is replaced by SQLCMD utility.
18. SQL SERVER Enterprise manager is now replaced by SQL SERVER Management studio.
19. SERVER Manager which was running in system tray is now replaced by SQL Computer manager.
20. Database mirror concept is supported in SQL SERVER 2005, which was not present in SQL SERVER 2000.
21. In SQL SERVER 2005 Indexes can be rebuilt online when the database is in actual production. If you look back in SQL SERVER 2000, you cannot do insert, update, and delete operations when you are building indexes.
22. (PG) Other than Serializable, Repeatable Read, Read Committed, and Read Uncommitted isolation levels, there is one more new isolation level “Snapshot Isolation level”.

Database questions -2

26. What is VDL (View Definition Language)?
It specifies user views and their mappings to the conceptual schema.

27. What is SDL (Storage Definition Language)?
This language is to specify the internal schema. This language may specify the mapping between two schemas.

28. What is Data Storage - Definition Language?
The storage structures and access methods used by database system are specified by a set of definition in a special type of DDL called data storage-definition language.

29. What is DML (Data Manipulation Language)?
This language that enable user to access or manipulate data as organised by appropriate data model.
Ø Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those data.
Ø Non-Procedural DML or High level: DML requires a user to specify what data are needed without specifying how to get those data.

30. What is DML Compiler?
It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand.

31. What is Query evaluation engine?
It executes low-level instruction generated by compiler.

33. What is DDL Interpreter?
It interprets DDL statements and record them in tables containing metadata.

34. What is Record-at-a-time?
The Low level or Procedural DML can specify and retrieve each record from a set of records. This retrieve of a record is said to be Record-at-a-time.

35. What is Set-at-a-time or Set-oriented?
The High level or Non-procedural DML can specify and retrieve many records in a single DML statement. This retrieve of a record is said to be Set-at-a-time or Set-oriented.

36. What is Relational Algebra?
It is procedural query language. It consists of a set of operations that take one or two relations as input and produce a new relation.

37. What is Relational Calculus?
It is an applied predicate calculus specifically tailored for relational databases proposed by E.F. Codd. E.g. of languages based on it are DSL ALPHA, QUEL.

38. How does Tuple-oriented relational calculus differ from domain-oriented relational calculus?
The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL
The domain-oriented calculus has domain variables i.e., variables that range over the underlying domains instead of over relation. E.g. ILL, DEDUCE.

39. What is normalization?
It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties
Ø Minimizing redundancy
Ø Minimizing insertion, deletion and update anomalies.

40. What is Functional Dependency?
A Functional dependency is denoted by X Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.

41. When is a functional dependency F said to be minimal?
Ø Every dependency in F has a single attribute for its right hand side.
Ø We cannot replace any dependency X A in F with a dependency Y A where Y is a proper subset of X and still have a set of dependency that is equivalent to F.
Ø We cannot remove any dependency from F and still have set of dependency that is equivalent to F.

42. What is Multivalued dependency?
Multivalued dependency denoted by X Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties
Ø t3

* = t4[X] = t1[X] = t2[X]

Ø t3[Y] = t1[Y] and t4[Y] = t2[Y]
Ø t3[Z] = t2[Z] and t4[Z] = t1[Z]
where [Z = (R-(X U Y)) ]

43. What is Lossless join property?
It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.

44. What is 1 NF (Normal Form)?
The domain of attribute must include only atomic (simple, indivisible) values.

45. What is Fully Functional dependency?
It is based on concept of full functional dependency. A functional dependency X Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.

46. What is 2NF?
A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.

47. What is 3NF?
A relation schema R is in 3NF if it is in 2NF and for every FD X A either of the following is true
Ø X is a Super-key of R.
Ø A is a prime attribute of R.
In other words, if every non prime attribute is non-transitively dependent on primary key.

48. What is BCNF (Boyce-Codd Normal Form)?
A relation schema R is in BCNF if it is in 3NF and satisfies an additional constraint that for every FD X A, X must be a candidate key.

49. What is 4NF?
A relation schema R is said to be in 4NF if for every Multivalued dependency X Y that holds over R, one of following is true
Ø X is subset or equal to (or) XY = R.
Ø X is a super key.

50. What is 5NF?
A Relation schema R is said to be 5NF if for every join dependency {R1, R2, ..., Rn} that holds R, one the following is true
Ø Ri = R for some i.
Ø The join dependency is implied by the set of FD, over R in which the left side is key of R.

Database Question -1

1. What is database?
A database is a logically coherent collection of data with some inherent meaning, representing some aspect of real world and which is designed, built and populated with data for a specific purpose.

2. What is DBMS?
It is a collection of programs that enables user to create and maintain a database. In other words it is general-purpose software that provides the users with the processes of defining, constructing and manipulating the database for various applications.

3. What is a Database system?
The database and DBMS software together is called as Database system.

4. Advantages of DBMS?
Ø Redundancy is controlled.
Ø Unauthorised access is restricted.
Ø Providing multiple user interfaces.
Ø Enforcing integrity constraints.
Ø Providing backup and recovery.

5. Disadvantage in File Processing System?
Ø Data redundancy & inconsistency.
Ø Difficult in accessing data.
Ø Data isolation.
Ø Data integrity.
Ø Concurrent access is not possible.
Ø Security Problems.

6. Describe the three levels of data abstraction?
The are three levels of abstraction:
Ø Physical level: The lowest level of abstraction describes how data are stored.
Ø Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data.
Ø View level: The highest level of abstraction describes only part of entire database.

7. Define the "integrity rules"
There are two Integrity rules.
Ø Entity Integrity: States that "Primary key cannot have NULL value"
Ø Referential Integrity: States that "Foreign Key can be either a NULL value or should be Primary Key value of other relation.

8. What is extension and intension?
Extension -
It is the number of tuples present in a table at any instance. This is time dependent.
Intension -
It is a constant value that gives the name, structure of table and the constraints laid on it.

9. What is System R? What are its two major subsystems?
System R was designed and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its purpose was to demonstrate that it is possible to build a Relational System that can be used in a real life environment to solve real life problems, with performance at least comparable to that of existing system.
Its two subsystems are
Ø Research Storage
Ø System Relational Data System.

10. How is the data structure of System R different from the relational structure?
Unlike Relational systems in System R
Ø Domains are not supported
Ø Enforcement of candidate key uniqueness is optional
Ø Enforcement of entity integrity is optional
Ø Referential integrity is not enforced

11. What is Data Independence?
Data independence means that "the application is independent of the storage structure and access strategy of data". In other words, The ability to modify the schema definition in one level should not affect the schema definition in the next higher level.
Two types of Data Independence:
Ø Physical Data Independence: Modification in physical level should not affect the logical level.
Ø Logical Data Independence: Modification in logical level should affect the view level.
NOTE: Logical Data Independence is more difficult to achieve

12. What is a view? How it is related to data independence?
A view may be thought of as a virtual table, that is, a table that does not really exist in its own right but is instead derived from one or more underlying base table. In other words, there is no stored file that direct represents the view instead a definition of view is stored in data dictionary.
Growth and restructuring of base tables is not reflected in views. Thus the view can insulate users from the effects of restructuring and growth in the database. Hence accounts for logical data independence.

13. What is Data Model?
A collection of conceptual tools for describing data, data relationships data semantics and constraints.

14. What is E-R model?
This data model is based on real world that consists of basic objects called entities and of relationship among these objects. Entities are described in a database by a set of attributes.

15. What is Object Oriented model?
This model is based on collection of objects. An object contains values stored in instance variables with in the object. An object also contains bodies of code that operate on the object. These bodies of code are called methods. Objects that contain same types of values and the same methods are grouped together into classes.

16. What is an Entity?
It is a 'thing' in the real world with an independent existence.

17. What is an Entity type?
It is a collection (set) of entities that have same attributes.

18. What is an Entity set?
It is a collection of all entities of particular entity type in the database.

19. What is an Extension of entity type?
The collections of entities of a particular entity type are grouped together into an entity set.

20. What is Weak Entity set?
An entity set may not have sufficient attributes to form a primary key, and its primary key compromises of its partial key and primary key of its parent entity, then it is said to be Weak Entity set.

21. What is an attribute?
It is a particular property, which describes the entity.

22. What is a Relation Schema and a Relation?
A relation Schema denoted by R(A1, A2, …, An) is made up of the relation name R and the list of attributes Ai that it contains. A relation is defined as a set of tuples. Let r be the relation which contains set tuples (t1, t2, t3, ..., tn). Each tuple is an ordered list of n-values t=(v1,v2, ..., vn).

23. What is degree of a Relation?
It is the number of attribute of its relation schema.

24. What is Relationship?
It is an association among two or more entities.

25. What is Relationship set?
The collection (or set) of similar relationships.

26. What is Relationship type?
Relationship type defines a set of associations or a relationship set among a given set of entity types.

27. What is degree of Relationship type?
It is the number of entity type participating.

28. What is DDL (Data Definition Language)?
A data base schema is specifies by a set of definitions expressed by a special language called DDL.