Microsoft SQL Server Interview Questions and answers

What is log shipping?
Log shipping is the process of automating the backup of database andtransaction log files on a production SQL server, and then restoringthem onto a standby server. Enterprise Editions only supports logshipping. In log shipping the transactional log file from one server isautomatically updated into the backup database on the other server. Ifone server fails, the other server will have the same db can be usedthis as the Disaster Recovery plan. The key feature of log shipping isthat is will automatically backup transaction logs throughout the dayand automatically restore them on the standby server at definedinterval.

What is the difference between a local and a global variable?
A local temporary table exists only for the duration of a connectionor, if defined inside a compound statement, for the duration of thecompound statement.
A global temporary table remains in thedatabase permanently, but the rows exist only within a givenconnection. When connection are closed, the data in the globaltemporary table disappears. However, the table definition remains withthe database for access when database is opened next time

What command do we use to rename a db?
sp_renamedb ‘oldname’ , ‘newname’
If someone is using db it will not accept sp_renmaedb. In that casefirst bring db to single user using sp_dboptions. Use sp_renamedb torename database. Use sp_dboptions to bring database to multi user mode.

What is sp_configure commands and set commands?
Use sp_configure to display or change server-level settings. To changedatabase-level settings, use ALTER DATABASE. To change settings thataffect only the current user session, use the SET statement.

Using query analyzer, name 3 ways to get an accurate count of the number of records in a table?
SELECT * FROM table1
SELECT COUNT(*) FROM table1
SELECT rows FROM sysindexes WHERE id = OBJECT_ID(table1) AND indid < 2

What are primary keys and foreign keys?
Primary keys are the unique identifiers for each row. They must containunique values and cannot be null. Due to their importance in relationaldatabases, Primary keys are the most fundamental of all keys andconstraints. A table can have only one Primary key.
Foreign keys are both a method of ensuring data integrity and a manifestation of the relationship between tables.

What is data integrity? Explain constraints?
Data integrity is an important feature in SQL Server. When usedproperly, it ensures that data is accurate, correct, and valid. It alsoacts as a trap for otherwise undetectable bugs within applications.
A PRIMARY KEY constraint is a unique identifier for a row within adatabase table. Every table should have a primary key constraint touniquely identify each row and only one primary key constraint can becreated for each table. The primary key constraints are used to enforceentity integrity.

A UNIQUE constraint enforces the uniquenessof the values in a set of columns, so no duplicate values are entered.The unique key constraints are used to enforce entity integrity as theprimary key constraints.

A FOREIGN KEY constraint prevents anyactions that would destroy links between tables with the correspondingdata values. A foreign key in one table points to a primary key inanother table. Foreign keys prevent actions that would leave rows withforeign key values when there are no primary keys with that value. Theforeign key constraints are used to enforce referential integrity.

A CHECK constraint is used to limit the values that can be placed in acolumn. The check constraints are used to enforce domain integrity.

A NOT NULL constraint enforces that the column will not accept nullvalues. The not null constraints are used to enforce domain integrity,as the check constraints.

How to get @@error and @@rowcount at the same time?
If @@Rowcount is checked after Error checking statement then it willhave 0 as the value of @@Recordcount as it would have been reset.
And if @@Recordcount is checked before the error-checking statementthen @@Error would get reset. To get @@error and @@rowcount at the sametime do both in same statement and store them in local variable. SELECT@RC = @@ROWCOUNT, @ER = @@ERROR

What is Identity?
Identity(or AutoNumber) is a column that automatically generates numericvalues. A start and increment value can be set, but most DBA leavethese at 1. A GUID column also generates numbers, the value of thiscannot be controled. Identity/GUID columns do not need to be indexed.

What is BCP? When does it used?
BulkCopy is a tool used to copy huge amount of data from tables andviews. BCP does not copy the structures same as source to destination.

How do you load large data to the SQL server database?
BulkCopy is a tool used to copy huge amount of data from tables. BULKINSERT command helps to Imports a data file into a database table orview in a user-specified format.

Can we rewrite subqueries into simple select statements or with joins?
Subqueries can often be re-written to use a standard outer join,resulting in faster performance. As we may know, an outer join uses theplus sign (+) operator to tell the database to return all non-matchingrows with NULL values. Hence we combine the outer join with a NULL testin the WHERE clause to reproduce the result set without using asub-query.

Can SQL Servers linked to other servers like Oracle?
SQL Server can be lined to any server provided it has OLE-DB providerfrom Microsoft to allow a link. E.g. Oracle has a OLE-DB provider fororacle that Microsoft provides to add it as linked server to SQL Servergroup.

How to know which index a table is using?
SELECT table_name,index_name FROM user_constraints

How to copy the tables, schema and views from one SQL server to another?
Microsoft SQL Server 2000 Data Transformation Services (DTS) is a setof graphical tools and programmable objects that lets user extract,transform, and consolidate data from disparate sources into single ormultiple destinations.

What is Self Join?
This is aparticular case when one table joins to itself, with one or two aliasesto avoid confusion. A self join can be of any type, as long as thejoined tables are the same. A self join is rather unique in that itinvolves a relationship with only one table. The common example is whencompany have a hierarchal reporting structure whereby one member ofstaff reports to another.

What is Cross Join?
A cross jointhat does not have a WHERE clause produces the Cartesian product of thetables involved in the join. The size of a Cartesian product result setis the number of rows in the first table multiplied by the number ofrows in the second table. The common example is when company wants tocombine each product with a pricing table to analyze each product ateach price.

Which virtual table does a trigger use?
Inserted and Deleted.

List few advantages of Stored Procedure.
Stored procedure can reduced network traffic and latency, boosting application performance.
Stored procedure execution plans can be reused, staying cached in SQL Server’s memory, reducing server overhead.
Stored procedures help promote code reuse.
Stored procedures can encapsulate logic. You can change stored procedure code without affecting clients.
Stored procedures provide better security to your data.



If I want to see what fields a table is made of, and what the sizes of the
fields are, what option do I have to look for?
• What is a query?
• A SQL query is typed in the _________ .
• What is the purpose of the model database?
• What is the purpose of the master database?
• What is the purpose of the tempdb database?
• What is the purpose of the USE command?
• If you delete a table in the database, will the data in the table be deleted too?
• What is the Parse Query button used for? How does this help you?
• Tables are created in a ____________________ in SQL Server 2005.
• What is usually the first word in a SQL query?
• Does a SQL Server 2005 SELECT statement require a FROM?
• Can a SELECT statement in SQL Server 2005 be used to make an assignment?
Explain with examples.
• What is the ORDER BY used for?
• Does ORDER BY actually change the order of the data in the tables or does it just
change the output?
• What is the default order of an ORDER BY clause?
• What kind of comparison operators can be used in a WHERE clause?
• What are four major operators that can be used to combine conditions on a WHERE
clause? Explain the operators with examples.
• What are the logical operators?
• In a WHERE clause, do you need to enclose a text column in quotes? Do you need to
enclose a numeric column in quotes?
• Is a null value equal to anything? Can a space in a column be considered a null
value? Why or why not?
• Will COUNT(column) include columns with null values in its count?
• What are column aliases? Why would you want to use column aliases? How can you
embed blanks in column aliases?
• What are table aliases?
• What are table qualifiers? When should table qualifiers be used?
• Are semicolons required at the end of SQL statements in SQL Server 2005?
• Do comments need to go in a special place in SQL Server 2005?
• When would you use the ROWCOUNT function versus using the WHERE clause?
• Is SQL case-sensitive? Is SQL Server 2005 case-sensitive?
• What is a synonym? Why would you want to create a synonym?
• Can a synonym name of a table be used instead of a table name in a SELECT
statement?
• Can a synonym of a table be used when you are trying to alter the definition
of a table?
• Can you type more than one query in the query editor screen at the same time?
• The INSERT INTO .. VALUES option will insert rows into the _________ of a table.
• While you are inserting values into a table with the INSERT INTO .. VALUES
option, does the order of the columns in the INSERT statement have to be the
same as the order of the columns in the table?
• While you are inserting values into a table with the INSERT INTO .. SELECT
option, does the order of the columns in the INSERT statement have to be
the same as the order of the columns in the table?
• When would you use an INSERT INTO .. SELECT option versus an INSERT INTO .. VALUES option? Give an example of each.
• What does the UPDATE command do?
• Can you change the data type of a column in a table after the table has been
created? If so,which command would you use?
• Will SQL Server 2005 allow you to reduce the size of a column?
• What integer data types are available in SQL Server 2005?
• What is the default value of an integer data type in SQL Server 2005?
• What decimal data types are available in SQL Server 2005?
• What is the difference between a CHAR and a VARCHAR datatype?
• Does Server SQL treat CHAR as a variable-length or fixed-length column?
Do other SQL implementations treat it in the same way?
• If you are going to have too many nulls in a column, what would be the best
data type to use?
• When columns are added to existing tables, what do they initially contain?
• What command would you use to add a column to a table in SQL Server?
• In SQL Server, which data type is used to store large object data types?
• If I do not need to store decimal places, what would be a good numeric data
type to use?
• I I need to store decimal places, but am not worried about rounding errors,
what would be a good data type to use?
• Should a column be defined as a FLOAT if it is going to be used as a primary key?
• What is a join? Why do you need a join?
• What is an INNER JOIN?
• Which clause[s] can be used in place of the JOIN in Server SQL?
• What is the Cartesian product?
• What would be the Cartesian product of a table with 15 rows and another table
with 23 rows?
• List some uses of the Cartesian product.
• What is an equi-join?
• What is a non-equi-join? Give an example of an non-equi-join.
• What is a self join? Give an example of a self join.
• What is a LEFT OUTER JOIN?
• What is a RIGHT OUTER JOIN?
• What is a CROSS JOIN?
• What is a FULL OUTER JOIN?


• Does Server SQL allow the use of *= to perform outer joins?
• What is the maximum number of rows that a self join can produce?
• For what kinds of joins will the associative property hold?
• What would be the Cartesian product of the two sets {a,b,c} and {c,d,e}?
• What are functions?
• What are aggregate functions? Give examples of aggregate functions.
What is another term for an aggregate function?
• What are row-level functions? Give examples of row-level functions.
• Is COUNT an aggregate function or a row-level function? Explain why.
Give at least one example of when the COUNT function may come in handy.
Does the COUNT function take nulls into account?
• Is AVG an aggregate function or a row-level function?
• What is the NULLIF function? Explain.
• How are ties handled in SQL Server?
• How does the DISTINCT function work?
• Are string functions (for example, SUBSTRING, RIGHT, LTRIM) aggregate
functions or row- level functions?
• What is the SUBSTRING function used for?
• What is the CHARINDEX function used for?
• What function would you use to find the leftmost characters in a string?
• What are the LTRIM/RTRIM functions used for?
• What function would produce the output in all lowercase?
• What function would you use to find the length of a string?
• What characters or symbols are most commonly used as wildcard characters in
SQL Server 2005?
• What is the concatenation operator in Server SQL 2005?
• What does the YEAR function do?
• What does the MONTH function do?
• What does the GEtdATE function do?
• What will the following query produce in SQL Server 2005?
o SELECT ('.....'+ names) AS [names]
o FROM Employee

• Does Server SQL allow an expression like COUNT(DISTINCT column_name)?
• How is the ISNULL function different from the NULLIF function?
• What function would you use to round a value to three decimal places?
• Which functions can the WITH TIES option be used with?
• What clause does the WITH TIES option require?
• What is the default date format in SQL Server 2005?
• How do dates have to be entered in Server SQL 2005?
• What function is used to convert between data types?
• What function is useful for formatting numbers?
• What function is useful for formatting dates?
• Which has precedence, AND or OR?
• Why do we need derived structures?
• What is a view?
• List some advantages of using views.
• List some advantages of using temporary tables.
• Can temporary tables replace views in all cases?
• What is the difference between a view and temporary table?
• What is the difference between a local temporary table and global temporary table?
• If data is changed in a view, is it changed in the original table?
• If data is changed in a temporary table, does it automatically change data in
the original table?
• What happens to local temporary tables after the session has been ended?
• What happens to global temporary table after the session has been ended?
• Which type of temporary table has a system-generated suffix attached to it?
What does this suffix mean?
• Why are inline views helpful?
• In SQL Server, is the ORDER BY clause allowed during the creation of a view?
• Is SELECT INTO allowed in a view? Why or why not?
• Where is the data stored in a view?
• How do you delete views?
• How do you delete a temporary table?
• Do you need to delete a local temporary table? Why or why not?
• Which operators have the highest/lowest precedence?
• In SQL Server, if a column of FLOAT data type were divided by a column of REAL
data type,what data type would the resulting column have? (Hint: refer to the
section on Data Type Preference.)
• Is an ORDER BY clause necessary when you use a DISTINCT? Why or why not?
• What are the major differences between the UNION operation and the JOIN operation?
• What is the major difference between the UNION and the UNION ALL?
• What major set operator does SQL Server 2005 not have? How can these problems
be resolved?
• What does union compatibility mean?
• What data types are union-compatible?
• What is the maximum number of rows that can result from a UNION of two tablesone
with 5 rows and the other with 6 rows?
• How can a UNION be used to implement an outer join? Explain.
• Does SQL Server 2005 support the MINUS operation? How can this be resolved? Give examples.
• What is a full outer join? Does SQL Server 2005 directly support a full outer join?
• Do you need the same number of columns to perform a union?
• Do you need the same data types to perform a union?
• Do you need the same number of columns to perform a join?
• From the examples given in the chapter, what does the UNION JOIN appear to do?
• If a VARCHAR column were unioned with a CHAR column, what would the resulting
column be?
• What does set compatibility mean?
• What is the maximum number of rows that can result from a INTERSECT of two
tablesone with 5 rows and the other with 6 rows?
• Do you need the same number of columns to perform an INTERSECT operation?
• Do you need the same data types to perform an INTERSECT operation?
• What is a subquery?
• Which part of the query/subquery is considered the inner query, and which part
is considered the outer query?
• Can a subquery always be done as a join? Why or why not?
• When writing a query that will have a subquery, how do you determine which
table/tables will go in the outer query?
• Which predicate can usually be reformulated into a join?
• When using operators, are many values acceptable from a result of a subquery?
• What can you do to insure a working subquery?
• What do aggregate functions do?
• How does the GROUP BY clause work?
• What is the difference between a GROUP BY and ORDER BY?
• What is the HAVING clause used for?
• Can the WHERE clause always be considered a substitute for the HAVING clause? Why or why not?
• Do functions of functions have to be handled in a special way in Server SQL 2005?
• Will nulls in grouped columns be included in a result set?
• How do aggregate functions treat nulls?
• Does the sequence of the columns in a GROUP BY clause have an effect on the end result?
• When would it not make sense to use the GROUP BY and DISTINCT functions together?
• Is GROUP BY affected by nulls?
• Which comes first in a SELECT statement, an ORDER BY or GROUP BY? Why?
• The GROUP BY and ________________ clauses are used together.
• What is a noncorrelated subquery?
• Which type of subquery can be executed on its own?
• Which part of a query is evaluated first, the query or the subquery?
• What are correlated subqueries?
• What does the EXISTS predicate do?
• What are considered universal qualifiers?
• Is correlation necessary when we use EXISTS? Why?
• Explain how the "for all" type SQL query involves a double-nested correlated subquery using the NOT EXISTS predicate.
• What is an index?
• Does an index slow down updates on indexed columns?
• What is a constraint?
• How many indexes does SQL Server 2005 allow you to have on a table?
• What command would you use to create an index?
• Is there a difference between an index and a constraint?
• What is the default ordering that will be created by an index (ascending or descending)?
• When can the UNIQUE option be used?
• What does the IGNORE NULL option do?
• How do you delete an index?
• What does the NOT NULL constraint do?
• What command must you use to include the NOT NULL constraint after a table has already been created?
• When a PRIMARY KEY constraint is included in a table, what other constraints does this imply?
• What is a concatenated primary key?
• How are the UNIQUE and PRIMARY KEY constraints different?
• What is a referential integrity constraint? What two keys does the referential integrity constraint usually include?
• What is a foreign key?
• What does the ON DELETE CASCADE option do?
• What does the ON UPDATE NO ACTION do?
• Can you use the ON DELETE and ON UPDATE in the same constraint?

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SQL Server Interview Questions and Answer I

What is log shipping? Can we do logshipping with SQL Server 7.0 -Logshipping is a new feature of SQL Server 2000. We should have two SQLServer - Enterprise Editions. From Enterprise Manager we can configurethe logshipping. In logshipping the transactional log file from oneserver is automatically updated into the backup database on the otherserver. If one server fails, the other server will have the same db andwe can use this as the DR (disaster recovery) plan.
Letus say the SQL Server crashed and you are rebuilding the databasesincluding the master database what procedure to you follow? - Forrestoring the master db we have to stop the SQL Server first and thenfrom command line we can type SQLSERVER –m which will basically bringit into the maintenance mode after which we can restore the master db.
Let us say master db itself has no backup. Now you have to rebuild the db so what kind of action do you take?

Whatis BCP? When do we use it? - BulkCopy is a tool used to copy hugeamount of data from tables and views. But it won’t copy the structuresof the same.

What should we do to copy the tables, schema andviews from one SQL Server to another? - We have to write some DTSpackages for it.

What are the different types of joins and what dies each do? What are the four main query statements?

-What is RDBMS?
RelationalData Base Management Systems (RDBMS) are database management systemsthat maintain data records and indices in tables. Relationships may becreated and maintained across and among the data and tables. In arelational database, relationships between data items are expressed bymeans of tables. Interdependencies among these tables are expressed bydata values rather than by pointers. This allows a high degree of dataindependence. An RDBMS has the capability to recombine the data itemsfrom different files, providing powerful tools for data usage.

What is normalization?
Databasenormalization is a data design and organization process applied to datastructures based on rules that help build relational databases. Inrelational database design, the process of organizing data to minimizeredundancy. Normalization usually involves dividing a database into twoor more tables and defining relationships between the tables. Theobjective is to isolate data so that additions, deletions, andmodifications of a field can be made in just one table and thenpropagated through the rest of the database via the definedrelationships.

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

What is Trigger?
Atrigger is a SQL procedure that initiates an action when an event(INSERT, DELETE or UPDATE) occurs. Triggers are stored in and managedby the DBMS.Triggers are used to maintain the referential integrity ofdata by changing the data in a systematic fashion. A trigger cannot becalled or executed; the DBMS automatically fires the trigger as aresult of a data modification to the associated table. Triggers can beviewed as similar to stored procedures in that both consist ofprocedural logic that is stored at the database level. Storedprocedures, however, are not event-drive and are not attached to aspecific table as triggers are. Stored procedures are explicitlyexecuted by invoking a CALL to the procedure while triggers areimplicitly executed. In addition, triggers can also execute storedprocedures.
Nested Trigger: A trigger can also contain INSERT,UPDATE and DELETE logic within itself, so when the trigger is firedbecause of data modification it can also cause another datamodification, thereby firing another trigger. A trigger that containsdata modification logic within itself is called a nested trigger.

What is View?
Asimple view can be thought of as a subset of a table. It can be usedfor retrieving data, as well as updating or deleting rows. Rows updatedor deleted in the view are updated or deleted in the table the view wascreated with. It should also be noted that as data in the originaltable changes, so does data in the view, as views are the way to lookat part of the original table. The results of using a view are notpermanently stored in the database. The data accessed through a view isactually constructed using standard T-SQL select command and can comefrom one to many different base tables or even other views.

What is Index?
Anindex is a physical structure containing pointers to the data. Indicesare created in an existing table to locate rows more quickly andefficiently. It is possible to create an index on one or more columnsof a table, and each index is given a name. The users cannot see theindexes, they are just used to speed up queries. Effective indexes areone of the best ways to improve performance in a database application.A table scan happens when there is no index available to help a query.In a table scan SQL Server examines every row in the table to satisfythe query results. Table scans are sometimes unavoidable, but on largetables, scans have a terrific impact on performance.

Clusteredindexes define the physical sorting of a database table’s rows in thestorage media. For this reason, each database table may have only oneclustered index.
Non-clustered indexes are created outside of the database table and contain a sorted list of references to the table itself.

What is the difference between clustered and a non-clustered index?
Aclustered index is a special type of index that reorders the wayrecords in the table are physically stored. Therefore table can haveonly one clustered index. The leaf nodes of a clustered index containthe data pages.

A nonclustered index is a special type of indexin which the logical order of the index does not match the physicalstored order of the rows on disk. The leaf node of a nonclustered indexdoes not consist of the data pages. Instead, the leaf nodes containindex rows.

What are the different index configurations a table can have?
A table can have one of the following index configurations:

No indexes
A clustered index
A clustered index and many nonclustered indexes
A nonclustered index
Many nonclustered indexes

What is cursors?
Cursoris a database object used by applications to manipulate data in a seton a row-by-row basis, instead of the typical SQL commands that operateon all the rows in the set at one time.

In order to work with a cursor we need to perform some steps in the following order:

Declare cursor
Open cursor
Fetch row from the cursor
Process fetched row
Close cursor
Deallocate cursor

What is the use of DBCC commands?
DBCCstands for database consistency checker. We use these commands to checkthe consistency of the databases, i.e., maintenance, validation taskand status checks.
E.g. DBCC CHECKDB - Ensures that tables in the db and the indexes are correctly linked.
DBCC CHECKALLOC - To check that all pages in a db are correctly allocated.
DBCC CHECKFILEGROUP - Checks all tables file group for any damage.

What is a Linked Server?
LinkedServers is a concept in SQL Server by which we can add other SQL Serverto a Group and query both the SQL Server dbs using T-SQL Statements.With a linked server, you can create very clean, easy to follow, SQLstatements that allow remote data to be retrieved, joined and combinedwith local data.
Storped Procedure sp_addlinkedserver, sp_addlinkedsrvlogin will be used add new Linked Server.

What is Collation?
Collationrefers to a set of rules that determine how data is sorted andcompared. Character data is sorted using rules that define the correctcharacter sequence, with options for specifying case-sensitivity,accent marks, kana character types and character width.

What are different type of Collation Sensitivity?
Case sensitivity
A and a, B and b, etc.

Accent sensitivity
a and á, o and ó, etc.

Kana Sensitivity
When Japanese kana characters Hiragana and Katakana are treated differently, it is called Kana sensitive.

Width sensitivity
Whena single-byte character (half-width) and the same character whenrepresented as a double-byte character (full-width) are treateddifferently then it is width sensitive.

What’s the difference between a primary key and a unique key?
Bothprimary key and unique enforce uniqueness of the column on which theyare defined. But by default primary key creates a clustered index onthe column, where are unique creates a nonclustered index by default.Another major difference is that, primary key doesn’t allow NULLs, butunique key allows one NULL only.

How to implement one-to-one, one-to-many and many-to-many relationships while designing tables?
One-to-Onerelationship can be implemented as a single table and rarely as twotables with primary and foreign key relationships.
One-to-Many relationships are implemented by splitting the data into two tables with primary key and foreign key relationships.
Many-to-Manyrelationships are implemented using a junction table with the keys fromboth the tables forming the composite primary key of the junction table.

What is a NOLOCK?
Usingthe NOLOCK query optimiser hint is generally considered good practicein order to improve concurrency on a busy system. When the NOLOCK hintis included in a SELECT statement, no locks are taken when data isread. The result is a Dirty Read, which means that another processcould be updating the data at the exact time you are reading it. Thereare no guarantees that your query will retrieve the most recent data.The advantage to performance is that your reading of data will notblock updates from taking place, and updates will not block yourreading of data. SELECT statements take Shared (Read) locks. This meansthat multiple SELECT statements are allowed simultaneous access, butother processes are blocked from modifying the data. The updates willqueue until all the reads have completed, and reads requested after theupdate will wait for the updates to complete. The result to your systemis delay(blocking).

What is difference between DELETE & TRUNCATE commands?
Deletecommand removes the rows from a table based on the condition that weprovide with a WHERE clause. Truncate will actually remove all the rowsfrom a table and there will be no data in the table after we run thetruncate command.

TRUNCATE
TRUNCATE is faster and uses fewer system and transaction log resources than DELETE.
TRUNCATEremoves the data by deallocating the data pages used to store thetable’s data, and only the page deallocations are recorded in thetransaction log.
TRUNCATE removes all rows from a table, but thetable structure and its columns, constraints, indexes and so on remain.The counter used by an identity for new rows is reset to the seed forthe column.
You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint.
Because TRUNCATE TABLE is not logged, it cannot activate a trigger.
TRUNCATE can not be Rolled back using logs.
TRUNCATE is DDL Command.
TRUNCATE Resets identity of the table.

DELETE
DELETE removes rows one at a time and records an entry in the transaction log for each deleted row.
Ifyou want to retain the identity counter, use DELETE instead. If youwant to remove table definition and its data, use the DROP TABLEstatement.
DELETE Can be used with or without a WHERE clause
DELETE Activates Triggers.
DELETE Can be Rolled back using logs.
DELETE is DML Command.
DELETE does not reset identity of the table.

Difference between Function and Stored Procedure?
UDF can be used in the SQL statements anywhere in the WHERE/HAVING/SELECT section where as Stored procedures cannot be.
UDFs that return tables can be treated as another rowset. This can be used in JOINs with other tables.
Inline UDF’s can be though of as views that take parameters and can be used in JOINs and other Rowset operations.

When is the use of UPDATE_STATISTICS command?
Thiscommand is basically used when a large processing of data has occurred.If a large amount of deletions any modification or Bulk Copy into thetables has occurred, it has to update the indexes to take these changesinto account. UPDATE_STATISTICS updates the indexes on these tablesaccordingly.

What types of Joins are possible with Sql Server?
Joinsare used in queries to explain how different tables are related. Joinsalso let you select data from a table depending upon data from anothertable.
Types of joins: INNER JOINs, OUTER JOINs, CROSS JOINs. OUTERJOINs are further classified as LEFT OUTER JOINS, RIGHT OUTER JOINS andFULL OUTER JOINS.

What is the difference between a HAVING CLAUSE and a WHERE CLAUSE?
Specifiesa search condition for a group or an aggregate. HAVING can be used onlywith the SELECT statement. HAVING is typically used in a GROUP BYclause. When GROUP BY is not used, HAVING behaves like a WHERE clause.Having Clause is basically used only with the GROUP BY function in aquery. WHERE Clause is applied to each row before they are part of theGROUP BY function in a query. HAVING criteria is applied after the thegrouping of rows has occurred.

What is sub-query? Explain properties of sub-query.
Sub-queriesare often referred to as sub-selects, as they allow a SELECT statementto be executed arbitrarily within the body of another SQL statement. Asub-query is executed by enclosing it in a set of parentheses.Sub-queries are generally used to return a single row as an atomicvalue, though they may be used to compare values against multiple rowswith the IN keyword.

A subquery is a SELECT statement that isnested within another T-SQL statement. A subquery SELECT statement ifexecuted independently of the T-SQL statement, in which it is nested,will return a result set. Meaning a subquery SELECT statement canstandalone and is not depended on the statement in which it is nested.A subquery SELECT statement can return any number of values, and can befound in, the column list of a SELECT statement, a FROM, GROUP BY,HAVING, and/or ORDER BY clauses of a T-SQL statement. A Subquery canalso be used as a parameter to a function call. Basically a subquerycan be used anywhere an expression can be used.

Properties of Sub-Query
A subquery must be enclosed in the parenthesis.
A subquery must be put in the right hand of the comparison operator, and
A subquery cannot contain a ORDER-BY clause.
A query can contain more than one sub-queries.

What are types of sub-queries?
Single-row subquery, where the subquery returns only one row.
Multiple-row subquery, where the subquery returns multiple rows,.and
Multiple column subquery, where the subquery returns multiple columns.

What is User Defined Functions?
User-DefinedFunctions allow to define its own T-SQL functions that can accept 0 ormore parameters and return a single scalar data value or a table datatype.

What kind of User-Defined Functions can be created?
Thereare three types of User-Defined functions in SQL Server 2000 and theyare Scalar, Inline Table-Valued and Multi-statement Table-valued.

Scalar User-Defined Function
AScalar user-defined function returns one of the scalar data types.Text, ntext, image and timestamp data types are not supported. Theseare the type of user-defined functions that most developers are used toin other programming languages. You pass in 0 to many parameters andyou get a return value.

Inline Table-Value User-Defined Function
AnInline Table-Value user-defined function returns a table data type andis an exceptional alternative to a view as the user-defined functioncan pass parameters into a T-SQL select command and in essence provideus with a parameterized, non-updateable view of the underlying tables.

Multi-statement Table-Value User-Defined Function
AMulti-Statement Table-Value user-defined function returns a table andis also an exceptional alternative to a view as the function cansupport multiple T-SQL statements to build the final result where theview is limited to a single SELECT statement. Also, the ability to passparameters into a T-SQL select command or a group of them gives us thecapability to in essence create a parameterized, non-updateable view ofthe data in the underlying tables. Within the create function commandyou must define the table structure that is being returned. Aftercreating this type of user-defined function, It can be used in the FROMclause of a T-SQL command unlike the behavior found when using a storedprocedure which can also return record sets.

Which TCP/IP port does SQL Server run on? How can it be changed?
SQLServer runs on port 1433. It can be changed from the Network UtilityTCP/IP properties –> Port number.both on client and the server.

What are the authentication modes in SQL Server? How can it be changed?
Windows mode and mixed mode (SQL & Windows).

Tochange authentication mode in SQL Server click Start, Programs,Microsoft SQL Server and click SQL Enterprise Manager to run SQLEnterprise Manager from the Microsoft SQL Server program group. Selectthe server then from the Tools menu select SQL Server ConfigurationProperties, and choose the Security page.

Where are SQL server users names and passwords are stored in sql server?
They get stored in master db in the sysxlogins table.

Which command using Query Analyzer will give you the version of SQL server and operating system?
SELECT SERVERPROPERTY('productversion'), SERVERPROPERTY ('productlevel'), SERVERPROPERTY ('edition')

What is SQL server agent?
SQLServer agent plays an important role in the day-to-day tasks of adatabase administrator (DBA). It is often overlooked as one of the maintools for SQL Server management. Its purpose is to ease theimplementation of tasks for the DBA, with its full-function schedulingengine, which allows you to schedule your own jobs and scripts.

Can a stored procedure call itself or recursive stored procedure? How many level SP nesting possible?
Yes.Because Transact-SQL supports recursion, you can write storedprocedures that call themselves. Recursion can be defined as a methodof problem solving wherein the solution is arrived at by repetitivelyapplying it to subsets of the problem. A common application ofrecursive logic is to perform numeric computations that lend themselvesto repetitive evaluation by the same processing steps. Storedprocedures are nested when one stored procedure calls another orexecutes managed code by referencing a CLR routine, type, or aggregate.You can nest stored procedures and managed code references up to 32levels.

What is @@ERROR?
The @@ERROR automatic variablereturns the error code of the last Transact-SQL statement. If there wasno error, @@ERROR returns zero. Because @@ERROR is reset after eachTransact-SQL statement, it must be saved to a variable if it is neededto process it further after checking it.

What is Raiseerror?
Storedprocedures report errors to client applications via the RAISERRORcommand. RAISERROR doesn’t change the flow of a procedure; it merelydisplays an error message, sets the @@ERROR automatic variable, andoptionally writes the message to the SQL Server error log and the NTapplication event log.

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SQL Server Interview Questions And Answers

What is normalization? - Well arelational database is basically composed of tables that containrelated data. So the Process of organizing this data into tables isactually referred to as normalization.

Whatis a Stored Procedure? - Its nothing but a set of T-SQL statementscombined to perform a single task of several tasks. Its basically likea Macro so when you invoke the Stored procedure, you actually run a setof statements. Can you give an example of Stored Procedure? - sp_helpdb, sp_who2, sp_renamedb are a set of system defined stored procedures.We can also have user defined stored procedures which can be called insimilar way.

What is a trigger? -
Triggers are basically usedto implement business rules. Triggers is also similar to storedprocedures. The difference is that it can be activated when data isadded or edited or deleted from a table in a database.

What is a view? -
If we have several tables in a db and we want to view only specificcolumns from specific tables we can go for views. It would also sufficethe needs of security some times allowing specfic users to see onlyspecific columns based on the permission that we can configure on theview. Views also reduce the effort that is required for writing queriesto access specific columns every time.
What is an Index? - Whenqueries are run against a db, an index on that db basically helps inthe way the data is sorted to process the query for faster and dataretrievals are much faster when we have an index.

What are the types of indexes available with SQL Server?
- There are basically two types of indexes that we use with the SQL Server. Clustered and the Non-Clustered.

What is the basic difference between clustered and a non-clustered index?
-The difference is that, Clustered index is unique for any given tableand we can have only one clustered index on a table. The leaf level ofa clustered index is the actual data and the data is resorted in caseof clustered index. Whereas in case of non-clustered index the leaflevel is actually a pointer to the data in rows so we can have as manynon-clustered indexes as we can on the db.

What are cursors?
-Well cursors help us to do an operation on a set of data that weretreive by commands such as Select columns from table. For example :If we have duplicate records in a table we can remove it by declaring acursor which would check the records during retreival one by one andremove rows which have duplicate values.

When do we use the UPDATE_STATISTICS command?
-This command is basically used when we do a large processing of data.If we do a large amount of deletions any modification or Bulk Copy intothe tables, we need to basically update the indexes to take thesechanges into account. UPDATE_STATISTICS updates the indexes on thesetables accordingly.

Which TCP/IP port does SQL Server run on?
- SQL Server runs on port 1433 but we can also change it for better security.

From where can you change the default port?
- From the Network Utility TCP/IP properties –> Port number.both on client and the server.

Can you tell me the difference between DELETE & TRUNCATE commands?
-Delete command removes the rows from a table based on the conditionthat we provide with a WHERE clause. Truncate will actually remove allthe rows from a table and there will be no data in the table after werun the truncate command.

Can we use Truncate command on a table which is referenced by FOREIGN KEY?
- No. We cannot use Truncate command on a table with Foreign Key because of referential integrity.

What is the use of DBCC commands?
-DBCC stands for database consistency checker. We use these commands tocheck the consistency of the databases, i.e., maintenance, validationtask and status checks.

Can you give me some DBCC command options?(Database consistency check)
-DBCC CHECKDB - Ensures that tables in the db and the indexes arecorrectly linked.and DBCC CHECKALLOC - To check that all pages in a dbare correctly allocated. DBCC SQLPERF - It gives report on currentusage of transaction log in percentage. DBCC CHECKFILEGROUP - Checksall tables file group for any damage.

What command do we use to rename a db? - sp_renamedb ‘oldname’ , ‘newname’
Wellsometimes sp_reanmedb may not work you know because if some one isusing the db it will not accept this command so what do you think youcan do in such cases? - In such cases we can first bring to db tosingle user using sp_dboptions and then we can rename that db and thenwe can rerun the sp_dboptions command to remove the single user mode.

What is the difference between a HAVING CLAUSE and a WHERE CLAUSE?
-Having Clause is basically used only with the GROUP BY function in aquery. WHERE Clause is applied to each row before they are part of theGROUP BY function in a query.

What do you mean by COLLATION?
-Collation is basically the sort order. There are three types of sortorder Dictionary case sensitive, Dictonary - case insensitive andBinary.

What is a Join in SQL Server?
- Join actually puts data from two or more tables into a single result set.

Canyou explain the types of Joins that we can have with Sql Server? -There are three types of joins: Inner Join, Outer Join, Cross Join

Whendo you use SQL Profiler? - SQL Profiler utility allows us to basicallytrack connections to the SQL Server and also determine activities suchas which SQL Scripts are running, failed jobs etc..

What is aLinked Server? - Linked Servers is a concept in SQL Server by which wecan add other SQL Server to a Group and query both the SQL Server dbsusing T-SQL Statements.
Can you link only other SQL Servers or anydatabase servers such as Oracle? - We can link any server provided wehave the OLE-DB provider from Microsoft to allow a link. For Oracle wehave a OLE-DB provider for oracle that microsoft provides to add it asa linked server to the sql server group.

Which stored procedure will you be running to add a linked server? - sp_addlinkedserver, sp_addlinkedsrvlogin

Whatare the OS services that the SQL Server installation adds? - MS SQLSERVER SERVICE, SQL AGENT SERVICE, DTC (Distribution transacco-ordinator)

Can you explain the role of each service? - SQLSERVER - is for running the databases SQL AGENT - is for automationsuch as Jobs, DB Maintanance, Backups DTC - Is for linking andconnecting to other SQL Servers

How do you troubleshoot SQLServer if its running very slow? - First check the processor and memoryusage to see that processor is not above 80% utilization and memory notabove 40-45% utilization then check the disk utilization usingPerformance Monitor, Secondly, use SQL Profiler to check for the usersand current SQL activities and jobs running which might be a problem.Third would be to run UPDATE_STATISTICS command to update the indexes
Letssay due to N/W or Security issues client is not able to connect toserver or vice versa. How do you troubleshoot? - First I will look toensure that port settings are proper on server and client Networkutility for connections. ODBC is properly configured at client end forconnection ——Makepipe & readpipe are utilities to check forconnection. Makepipe is run on Server and readpipe on client to checkfor any connection issues.

What are the authentication modes in SQL Server? - Windows mode and mixed mode (SQL & Windows).

Wheredo you think the users names and passwords will be stored in sqlserver? - They get stored in master db in the sysxlogins table.

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