SQL Server Interview Questions & Answers, Interview Questions and Answers for SQL Server

SQL Server is a relational database management system(RDBMS) produced by Microsoft. Its primary query language is Transact-SQL, an implementation of the ANSI/ISO standard Structured Query Language (SQL) used by both Microsoft and Sybase

What is RDBMS?

Relational Data Base Management Systems (RDBMS) are database management systems that maintain data records and indices in tables. Relationships may be created and maintained across and among the data and tables. In a relational database, relationships between data items are expressed by means of tables. Interdependencies among these tables are expressed by data values rather than by pointers. This allows a high degree of data independence. An RDBMS has the capability to recombine the data items from different files, providing powerful tools for data usage.

What is normalization?

Database normalization is a data design and organization process applied to data structures based on rules that help build relational databases. In relational database design, the process of organizing data to minimize redundancy. Normalization usually involves dividing a database into two or more tables and defining relationships between the tables. The objective is to isolate data so that additions, deletions, and modifications of a field can be made in just one table and then propagated through the rest of the database via the defined relationships.

What are different normalization forms?

1NF: Eliminate Repeating Groups:- Make a separate table for each set of related attributes, and give each table a primary key. Each field contains at most one value from its attribute domain.
2NF: Eliminate Redundant Data:- If an attribute depends on only part of a multi-valued key, remove it to a separate table.
3NF: Eliminate Columns Not Dependent On Key:- If attributes do not contribute to a description of the key, remove them to a separate table. All attributes must be directly dependent on the primary key.
BCNF: Boyce-Codd Normal Form:- If there are non-trivial dependencies between candidate key attributes, separate them out into distinct tables.
4NF: Isolate Independent Multiple Relationships:- No table may contain two or more 1:n or n:m relationships that are not directly related.
5NF: Isolate Semantically Related Multiple Relationships:- There may be practical constrains on information that justify separating logically related many-to-many
relationships.
ONF: Optimal Normal Form:- A model limited to only simple (elemental) facts, as expressed in Object Role Model notation.
DKNF: Domain-Key Normal Form:- A model free from all modification anomalies.
Remember, these normalization guidelines are cumulative. For a database to be in 3NF, it must first fulfill all the criteria of a 2NF and 1NF database.

What is Stored Procedure?

A stored procedure is a named group of SQL statements that have been previously created and stored in the server database. Stored procedures accept input parameters so that a single procedure can be used over the network by several clients using different input data. And when the procedure is modified, all clients automatically get the new version. Stored procedures reduce network traffic and improve performance. Stored procedures can be used to help ensure the integrity of the database.
e.g. sp_helpdb, sp_renamedb, sp_depends etc.

What is Cascade and Restrict when we use DROP table in SQL SERVER ?

When we are using Drop table in SQL the syntax is simple.
Drop table table_name(CASCADE / RESTRICT)
We use cascade to drop table although it have some dependencies just like triggers,stroeprocrdure,primarykey,foreignkey it will delete first.
But if we use restrict a error message is shown on using of DROP if the table have relation Trigger,store procedure.

What is COMMIT & ROLLBACK statement in SQL ?

Commit statement helps in termination of the current transaction and do all the changes that occur in transaction persistent and this also commits all the changes to the database.COMMIT we can also use in store procedure.
ROLLBACK do the same thing just terminate the currenct transaction but one another thing is that the changes made to database are ROLLBACK to the database.

What is diffrence between OSQL and Query Analyzer?

Both are the same but ther eis little diffrence OSQL is command line tool whic is execute qery and display the result same a query analyzer but query analyzer is graphical and OSQL is a command line tool.OSQL have not ability like query analyzer to analyze queries and show statics on speed of execution and other usefull thing about OSQL is that its helps in scheduling.

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