Number:
|
1
|
Heading:
|
SQL Server
|
Question:
|
What is normalization? What are the different levels of
normalization?
|
Answer:
|
Normalizing a logical database design
involves using formal methods to separate the data into multiple, related
tables. A greater number of narrow tables (with fewer columns) is
characteristic of a normalized database. A few wide tables (with more
columns) is characteristic of an nonnomalized database.
|
Level:
|
SE/SSE
|
Number:
|
2
|
Heading:
|
SQL Server
|
Question:
|
What is denormalization and when would you go for it?
|
Answer:
|
As the name indicates, denormalization is the reverse process of
normalization. It's the controlled introduction of redundancy in to the
database design. It helps improve the query performance as the number of
joins could be reduced.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
3
|
Heading:
|
SQL Server
|
Question:
|
How do you implement one-to-one, one-to-many and many-to-many
relationships while designing tables?
|
Answer:
|
One-to-One relationship can be implemented as a single table and
rarely as two tables 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-Many relationships are implemented using a junction table with the keys from both the tables forming the composite primary key of the junction table. |
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
4
|
Heading:
|
SQL Server
|
Question:
|
What's the difference between a primary key and a unique key?
|
Answer:
|
Both
primary key and unique enforce uniqueness of the column on which they are
defined. But by default primary key creates a clustered index on the column,
where are unique creates a nonclustered index by default. Another major
difference is that, primary key doesn't allow NULLs, but unique key allows
one NULL only.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
5
|
Heading:
|
SQL Server
|
Question:
|
What are user defined datatypes and when you should go for them?
|
Answer:
|
User
defined datatypes let you extend the base SQL Server datatypes by providing a
descriptive name, and format to the database. Take for example, in your
database, there is a column called Flight_Num which appears in many tables.
In all these tables it should be varchar(8). In this case you could create a
user defined datatype called Flight_num_type of varchar(8) and use it across
all your tables.
|
Level:
|
SE/SSE
|
Number:
|
6
|
Heading:
|
SQL Server
|
Question:
|
What is bit datatype and what's the information that can be
stored inside a bit column?
|
Answer:
|
Bit
datatype is used to store boolean information like 1 or 0 (true or false).
Untill SQL Server 6.5 bit datatype could hold either a 1 or 0 and there was
no support for NULL. But from SQL Server 7.0 onwards, bit datatype can
represent a third state, which is NULL.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
7
|
Heading:
|
SQL Server
|
Question:
|
What are defaults? Is there a column to which a default can't be
bound
|
Answer:
|
A
default is a value that will be used by a column, if no value is supplied to
that column while inserting data. IDENTITY columns and timestamp columns
can't have defaults bound to them
|
Comments:
|
|
Level:
|
SE
|
Number:
|
8
|
Heading:
|
SQL Server
|
Question:
|
What is a transaction and what are ACID properties?
|
Answer:
|
A transaction is a logical unit of work in which, all the steps
must be performed or none. ACID stands for Atomicity, Consistency, Isolation,
Durability. These are the properties of a transaction
|
Level:
|
SE/SSE
|
Number:
|
9
|
Heading:
|
SQL Server
|
Question:
|
Explain different isolation levels
|
Answer:
|
An isolation level determines the degree of isolation of data
between concurrent transactions. The default SQL Server isolation level is
Read Committed. Here are the other isolation levels (in the ascending order
of isolation): Read Uncommitted, Read Committed, Repeatable Read,
Serializable. See SQL Server books online for an explanation of the isolation
levels. Be sure to read about SET TRANSACTION ISOLATION LEVEL, which lets you
customize the isolation level at the connection level.
|
Level:
|
SSE/TL
|
Number:
|
10
|
Heading:
|
SQL Server
|
Question:
|
CREATE INDEX myIndex ON myTable(myColumn)
What type of Index will get created after executing the above statement? |
Answer:
|
Non-clustered index. Important thing to note: By default a
clustered index gets created on the primary key, unless specified otherwise.
|
Comments:
|
If the candidate seems reasonably aware, ask him to explain the
scenarios of when to use clustered indexes and when to use non clustered
indexes.
|
Level:
|
SSE/TL
|
Number:
|
11
|
Heading:
|
SQL Server
|
Question:
|
What is lock escalation?
|
Answer:
|
Lock
escalation is the process of converting a lot of low level locks (like row
locks, page locks) into higher level locks (like table locks). Every lock is
a memory structure too many locks would mean, more memory being occupied by
locks. To prevent this from happening, SQL Server escalates the many
fine-grain locks to fewer coarse-grain locks. Lock escalation threshold was
definable in SQL Server 6.5, but from SQL Server 7.0 onwards it's dynamically
managed by SQL Server.
|
Level:
|
SSE/TL
|
Number:
|
12
|
|
Heading:
|
SQL Server
|
|
Question:
|
What's the difference between DELETE TABLE and TRUNCATE TABLE
commands?
|
|
Answer:
|
DELETE
TABLE is a logged operation, so the deletion of each row gets logged in the
transaction log, which makes it slow. TRUNCATE TABLE also deletes all the
rows in a table, but it won't log the deletion of each row, instead it logs
the deallocation of the data pages of the table, which makes it faster.
|
|
Number:
|
13
|
|
Heading:
|
SQL Server
|
|
Question:
|
What are constraints? Explain different types of constraints.
|
|
Answer:
|
Constraints
enable the RDBMS enforce the integrity of the database automatically, without
needing you to create triggers, rule or defaults.
Types of constraints: NOT NULL, CHECK, UNIQUE, PRIMARY KEY, FOREIGN KEY |
|
Comments:
|
||
Level:
|
SE/SSE
|
|
Number:
|
14
|
Heading:
|
SQL Server
|
Question:
|
Whar is an index? What are the types of indexes? How many
clustered indexes can be created on a table? I create a separate index on each
column of a table. what are the advantages and disadvantages of this
approach?
|
Answer:
|
Indexes
in SQL Server are similar to the indexes in books. They help SQL Server
retrieve the data quicker.
Indexes are of two types. Clustered indexes and non-clustered indexes. When you craete a clustered index on a table, all the rows in the table are stored in the order of the clustered index key. So, there can be only one clustered index per table. Non-clustered indexes have their own storage separate from the table data storage. Non-clustered indexes are stored as B-tree structures (so do clustered indexes), with the leaf level nodes having the index key and it's row locater. The row located could be the RID or the Clustered index key, depending up on the absence or presence of clustered index on the table. If you create an index on each column of a table, it improves the query performance, as the query optimizer can choose from all the existing indexes to come up with an efficient execution plan. At the same t ime, data modification operations (such as INSERT, UPDATE, DELETE) will become slow, as every time data changes in the table, all the indexes need to be updated. Another disadvantage is that, indexes need disk space, the more indexes you have, more disk space is used. |
Comments:
|
|
Level:
|
SSE/TL
|
Number:
|
15
|
Heading:
|
SQL Server
|
Question:
|
What is RAID and what are different types of RAID configurations?
|
Answer:
|
RAID stands for Redundant Array of Inexpensive Disks, used to
provide fault tolerance to database servers. There are six RAID levels 0
through 5 offering different levels of performance, fault tolerance
|
Comments:
|
Typically a DBA Question.
|
Level:
|
SSE/TL
|
Number:
|
16
|
Heading:
|
SQL Server
|
Question:
|
What are the steps you will take to improve performance of a poor
performing query?
|
Answer:
|
This is a very open ended question and there could be a lot of
reasons behind the poor performance of a query. But some general issues would
be: No indexes, table scans, missing or out of date statistics, blocking, excess
recompilations of stored procedures, procedures and triggers without SET
NOCOUNT ON, poorly written query with unnecessarily complicated joins, too
much normalization, excess usage of cursors and temporary tables.
Some of the tools/ways that help troubleshooting performance problems are: SET SHOWPLAN_ALL ON, SET SHOWPLAN_TEXT ON, SET STATISTICS IO ON, SQL Server Profiler, Windows NT /2000 Performance monitor, Graphical execution plan in Query Analyzer. |
Comments:
|
|
Level:
|
SSE/TL
|
Number:
|
17
|
Heading:
|
SQL Server
|
Question:
|
What is a deadlock and what is a live lock? How will you go about
resolving deadlocks?
|
Answer:
|
Deadlock is a situation when two processes, each having a lock
on one piece of data, attempt to acquire a lock on the other's piece. Each
process would wait indefinitely for the other to release the lock,
unless one of the user processes is terminated. SQL Server detects deadlocks
and terminates one user's process.
A livelock is one, where a request for an exclusive lock is repeatedly denied because a series of overlapping shared locks keeps interfering. SQL Server detects the situation after four denials and refuses further shared locks. A livelock also occurs when read transactions monopolize a table or page, forcing a write transaction to wait indefinitely. |
Comments:
|
|
Level:
|
SSE/TL
|
Number:
|
18
|
Heading:
|
SQL Server
|
Question:
|
What are statistics, under what circumstances they go out of
date, and how do you update them?
|
Answer:
|
Statistics
determine the selectivity of the indexes. If an indexed column has unique
values then the selectivity of that index is more, as opposed to an index
with non-unique values. Query optimizer uses these indexes in determining
whether to choose an index or not while executing a query.
Some situations under which you should update statistics: 1) If there is significant change in the key values in the index 2) If a large amount of data in an indexed column has been added, changed, or removed (that is, if the distribution of key values has changed), or the table has been truncated using the TRUNCATE TABLE statement and then repopulated 3) Database is upgraded from a previous version |
Comments:
|
Typically a DBA Question.
|
Level:
|
SSE/TL
|
Number:
|
19
|
Heading:
|
SQL Server
|
Question:
|
What are the different ways of moving data/databases between
servers and databases in SQL Server?
|
Answer:
|
There
are lots of options available, you have to choose your option depending upon
your requirements. Some of the options you have are: BACKUP/RESTORE,
dettaching and attaching databases, replication, DTS, BCP, logshipping,
INSERT...SELECT, SELECT...INTO, creating INSERT scripts to generate data.
|
Comments:
|
|
Level:
|
SSE/TL
|
Number:
|
20
|
Heading:
|
SQL Server
|
Question:
|
Explian different types of BACKUPs avaialabe in SQL Server? Given
a particular scenario, how would you go about choosing a backup plan?
|
Answer:
|
Types
of backups you can create in SQL Sever 7.0+ are Full database backup,
differential database backup, transaction log backup, filegroup backup
|
Comments:
|
Typically a DBA Question.
|
Level:
|
SSE/TL
|
Number:
|
21
|
Heading:
|
SQL Server
|
Question:
|
What is database replicaion? What are the different types of
replication you can set up in SQL Server?
|
Answer:
|
Replication
is the process of copying/moving data between databases on the same or
different servers. SQL Server supports the following types of replication
scenarios:
|
Comments:
|
Typically a DBA Question.
|
Level:
|
SSE/TL
|
Number:
|
22
|
Heading:
|
SQL Server
|
Question:
|
What are cursors? Explain different types of cursors. What are
the disadvantages of cursors? How can you avoid cursors?
|
Answer:
|
Cursors allow row-by-row
prcessing of the resultsets.
Types of cursors: Static, Dynamic, Forward-only, Keyset-driven. See books online for more information. Disadvantages of cursors: Each time you fetch a row from the cursor, it results in a network roundtrip, where as a normal SELECT query makes only one rowundtrip, however large the resultset is. Cursors are also costly because they require more resources and temporary storage (results in more IO operations). Furthere, there are restrictions on the SELECT statements that can be used with some types of cursors. Most of the times, set based operations can be used instead of cursors. Here is an example: If you have to give a flat hike to your employees using the following criteria: Salary between 30000 and 40000 -- 5000 hike Salary between 40000 and 55000 -- 7000 hike Salary between 55000 and 65000 -- 9000 hike In this situation many developers tend to use a cursor, determine each employee's salary and update his salary according to the above formula. But the same can be achieved by multiple update statements or can be combined in a single UPDATE statement as shown below: UPDATE tbl_emp SET salary = CASE WHEN salary BETWEEN 30000 AND 40000 THEN salary + 5000 WHEN salary BETWEEN 40000 AND 55000 THEN salary + 7000 WHEN salary BETWEEN 55000 AND 65000 THEN salary + 10000 END Another situation in which developers tend to use cursors: You need to call a stored procedure when a column in a particular row meets certain condition. You don't have to use cursors for this. This can be achieved using WHILE loop, as long as there is a unique key to identify each row |
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
23
|
Heading:
|
SQL Server
|
Question:
|
What is a join and explain different types of joins.
|
Answer:
|
Joins
are used in queries to explain how different tables are related. Joins also
let you select data from a table depending upon data from another table.
Types of joins: INNER JOINs, OUTER JOINs, CROSS JOINs. OUTER JOINs are further classified as LEFT OUTER JOINS, RIGHT OUTER JOINS and FULL OUTER JOINS. |
Number:
|
24
|
Heading:
|
SQL Server
|
Question:
|
What is an extended stored procedure? Can you instantiate a COM
object by using T-SQL?
|
Answer:
|
An extended stored procedure
is a function within a DLL (written in a programming language like C, C++
using Open Data Services (ODS) API) that can be called from T-SQL, just the
way we call normal stored procedures using the EXEC statement. See books
online to learn how to create extended stored procedures and how to add them
to SQL Server.
Yes, you can instantiate a COM (written in languages like VB, VC++) object from T-SQL by using sp_OACreate stored procedure. Also see books online for sp_OAMethod, sp_OAGetProperty, sp_OASetProperty, sp_OADestroy |
Comments:
|
|
Level:
|
SSE/TL
|
Number:
|
25
|
Heading:
|
SQL Server
|
Question:
|
How extended stored procedures work?
|
Answer:
|
The
process by which an extended stored procedure works is:
The
extended stored procedure passes result sets and return parameters back to
the server by using the Open Data Services API.
|
Comments:
|
|
Level:
|
SSE/TL
|
Number:
|
26
|
Heading:
|
SQL Server
|
Question:
|
What are triggers? How many triggers you can have on a table?
|
Answer:
|
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
27
|
Heading:
|
SQL Server
|
Question:
|
There is a trigger defined for INSERT operations on a table, in
an OLTP system. The trigger is written to instantiate a COM object and pass
the newly insterted rows to it for some custom processing. What do you think
of this implementation? Can this be implemented better?
|
Answer:
|
Instantiating COM objects is
a time consuming process and since you are doing it from within a trigger, it
slows down the data insertion process. Same is the case with sending emails
from triggers. This scenario can be better implemented by logging all the
necessary data into a separate table, and have a job which periodically
checks this table and does the needful.
|
Comments:
|
|
Level:
|
SSE/TL
|
Number:
|
28
|
Heading:
|
SQL Server
|
Question:
|
What is a self join? Explain it with an example.
|
Answer:
|
Self
join is just like any other join, except that two instances of the same table
will be joined in the query. Here is an example: Employees table which
contains rows for normal employees as well as managers. So, to find out the
managers of all the employees, you need a self join. CREATE TABLE emp ( empid int, mgrid int, empname char(10) ) INSERT emp SELECT 1,2,'Vyas' INSERT emp SELECT 2,3,'Mohan' INSERT emp SELECT 3,NULL,'Shobha' INSERT emp SELECT 4,2,'Shridhar' INSERT emp SELECT 5,2,'Sourabh' SELECT t1.empname [Employee], t2.empname [Manager] FROM emp t1, emp t2 WHERE t1.mgrid = t2.empid Here's an advanced query using a LEFT OUTER JOIN that even returns the employees without managers (super bosses) SELECT t1.empname [Employee], COALESCE(t2.empname, 'No manager') [Manager] FROM emp t1 LEFT OUTER JOIN emp t2 ON t1.mgrid = t2.empid |
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
29
|
Heading:
|
SQL Server
|
Question:
|
What are the benefits of Normalization?
|
Answer:
|
Some of
the benefits of normalization include:
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
30
|
Heading:
|
SQL Server
|
Question:
|
What are the disadvantages of Normalization?
|
Answer:
|
As normalization increases, so do the
number and complexity of joins required to retrieve data. Too many complex
relational joins between too many tables can hinder performance.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
31
|
Heading:
|
SQL Server
|
Question:
|
What are the different types of temporary tables?
|
Answer:
|
SQL
Server supports temporary tables. These tables have names that start with a
number sign (#). If a temporary table is not dropped when a user disconnects,
SQL Server automatically drops the temporary table. Temporary tables are not
stored in the current database; they are stored in the tempdb system
database. There are two types of temporary tables:
The names of these tables begin with one number
sign (#). These tables are visible only to the connection that created them.
The names of
these tables begin with two number signs (##). These tables are visible to
all connections. If the tables are not dropped explicitly before the
connection that created them disconnects, they are dropped as soon as all
other tasks stop referencing them. No new tasks can reference a global
temporary table after the connection that created it disconnects. The
association between a task and a table is always dropped when the current
statement completes executing; therefore, global temporary tables are usually
dropped soon after the connection that created them disconnects.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
32
|
Heading:
|
SQL Server
|
Question:
|
What is the role of master database?
|
Answer:
|
The master database records all of
the system level information for a SQL Server system. It records all login
accounts and all system configuration settings. master is the database
that records the existence of all other databases, including the location of
the database files. master records the initialization information for
SQL Server; always have a recent backup of master available.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
33
|
Heading:
|
SQL Server
|
Question:
|
What is the role of tempDB database?
|
Answer:
|
tempdb
holds all temporary tables and temporary stored procedures. It also fills any
other temporary storage needs such as work tables generated by SQL Server. tempdb
is a global resource; the temporary tables and stored procedures for all
users connected to the system are stored there. tempdb is re-created
every time SQL Server is started so the system starts with a clean copy of
the database. Because temporary tables and stored procedures are dropped
automatically on disconnect, and no connections are active when the system is
shut down, there is never anything in tempdb to be saved from one
session of SQL Server to another.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
34
|
Heading:
|
SQL Server
|
Question:
|
What is the role of model database?
|
Answer:
|
The model database is used as the
template for all databases created on a system. When a CREATE DATABASE
statement is issued, the first part of the database is created by copying in
the contents of the model database, then the remainder of the new
database is filled with empty pages. Because tempdb is created every
time SQL Server is started, the model database must always exist on a
SQL Server system.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
35
|
Heading:
|
SQL Server
|
Question:
|
What is the role of msdb database?
|
Answer:
|
The msdb database is used by SQL
Server Agent for scheduling alerts and jobs, and recording operators.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
36
|
Heading:
|
SQL Server
|
Question:
|
What are transaction logs?
|
Answer:
|
SQL Server uses the transaction log of
each database to recover transactions. The transaction log is a serial record
of all modifications that have occurred in the database as well as the
transaction that performed each modification. The transaction log records the
start of each transaction. It records the changes to the data and enough
information to undo the modifications (if necessary later) made during each
transaction. For some large operations, such as CREATE INDEX, the transaction
log instead records the fact that the operation took place. The log grows
continuously as logged operations occur in the database.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
37
|
Heading:
|
SQL Server
|
Question:
|
What is @@TRANCOUNT?
|
Answer:
|
Returns the number of active transactions
for the current connection.
The BEGIN TRANSACTION statement
increments @@TRANCOUNT by 1. ROLLBACK TRANSACTION decrements @@TRANCOUNT to
0, except for ROLLBACK TRANSACTION savepoint_name, which does not
affect @@TRANCOUNT. COMMIT TRANSACTION or COMMIT WORK decrement @@TRANCOUNT
by 1.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
38
|
Heading:
|
SQL Server
|
Question:
|
What is @@ERROR?
|
Answer:
|
Returns the error number for the last
Transact-SQL statement executed.
When Microsoft® SQL Server completes the
execution of a Transact-SQL statement, @@ERROR is set to 0 if the statement
executed successfully. If an error occurs, an error message is returned.
@@ERROR returns the number of the error message until another Transact-SQL
statement is executed. You can view the text associated with an @@ERROR error
number in the sysmessages system table.
Because @@ERROR is cleared and reset on
each statement executed, check it immediately following the statement
validated, or save it to a local variable that can be checked later.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
39
|
Heading:
|
SQL Server
|
Question:
|
What are the different authentication modes in SQL 2000?
|
Answer:
|
·
Windows Authentication
(Windows Authentication)
·
Mixed Mode Authentication
(Windows Authentication and SQL Server Authentication)
|
Comments:
|
If the candidate seems reasonably aware, ask him to explain the
guidelines for choosing one of the two authentication mechanisms.
|
Level:
|
SE/SSE
|
Number:
|
40
|
Heading:
|
SQL Server
|
Question:
|
What is windows authentication mode?
|
Answer:
|
Windows Authentication mode allows a user
to connect through a Microsoft Windows NT® 4.0 or Windows® 2000 user account.
When a user connects through a Windows NT
4.0 or Windows 2000 user account, SQL Server revalidates the account name and
password by calling back to Windows NT 4.0 or Windows 2000 for the
information.SQL Server achieves login security integration with Windows NT 4.0 or Windows 2000 by using the security attributes of a network user to control login access. A user's network security attributes are established at network login time and are validated by a Windows domain controller. When a network user tries to connect, SQL Server uses Windows-based facilities to determine the validated network user name. SQL Server then verifies that the person is who they say they are, and then permits or denies login access based on that network user name alone, without requiring a separate login name and password. |
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
41
|
Heading:
|
SQL Server
|
Question:
|
What is mixed mode authentication?
|
Answer:
|
When a user connects with a specified
login name and password from a nontrusted connection, SQL Server performs the
authentication itself by checking to see if a SQL Server login account has
been set up and if the specified password matches the one previously
recorded. If SQL Server does not have a login account set, authentication
fails and the user receives an error message.
|
Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
42
|
Heading:
|
SQL Server
|
Question:
|
What is the difference between Where Clause and Having Clause ?
|
Answer:
|
A
HAVING clause is like a WHERE clause, but applies only to groups as a whole (that
is, to the rows in the result set
representing groups), whereas the WHERE clause applies to individual rows. A
query can contain both a WHERE clause and a HAVING clause. In that case:
|
Comments:
|
|
Level:
|
SE
|
Number:
|
43
|
Heading:
|
SQL Server
|
Question:
|
What is TimeStamp data type ?
|
Answer:
|
Timestamp
is a data type that exposes automatically generated binary numbers,
which are guaranteed to be unique within a database. timestamp is used
typically as a mechanism for version-stamping table rows. The storage size is
8 bytes.
A table can have only one timestamp column.
The value in the timestamp column is updated every time a row
containing a timestamp column is inserted or updated
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Comments:
|
|
Level:
|
SE
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Number:
|
44
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Heading:
|
SQL Server
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Question:
|
How to retrieve Data in XML format using Select query?
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Answer:
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Retrieve XML data using the SELECT
statement and the FOR XML clause.
To
retrieve results directly, use the FOR XML clause of the SELECT statement,
and within the FOR XML clause, specify one of these XML modes:
These modes are in effect only
for the execution of the query for which they are set. They do not affect the
results of any subsequent queries. In addition to specifying the XML mode,
you can also request the XML-Data schema.
SELECT Customers.CustomerID, ContactName, CompanyName,
Orders.CustomerID, OrderDate
FROM Customers, Orders
WHERE Customers.CustomerID = Orders.CustomerID
AND (Customers.CustomerID = N'ALFKI'
OR Customers.CustomerID = N'XYZAA')
ORDER BY Customers.CustomerID
FOR XML AUTO
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Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
45
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Heading:
|
SQL Server
|
Question:
|
What is the use of OPENXML Function?
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Answer:
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Use the Transact-SQL OPENXML function to
insert data represented as an XML document. OPENXML is a rowset provider
similar to a table or a view, providing a rowset over in-memory XML
documents. OPENXML allows access to XML data as if it is a relational rowset
by providing a rowset view of the internal representation of an XML document.
The records in the rowset can be stored in database tables. OPENXML can be
used in SELECT, and SELECT INTO statements where a source table or view can
be specified.
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Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
46
|
Heading:
|
SQL Server
|
Question:
|
How to retrieve last inserted identity value?
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Answer:
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Use @@IDENTITY function to the get the
last-inserted identity value.
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Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
47
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Heading:
|
SQL Server
|
Question:
|
What are full text indexes?
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Answer:
|
A Microsoft SQL Server 2000 full-text
index provides efficient support for sophisticated word searches in character
string data. The full-text index stores information about significant words
and their location within a given column. This information is used to quickly
complete full-text queries that search for rows with particular words or
combinations of words.
Full-text support for Microsoft SQL
Server 2000 data involves two features: the ability to issue queries against
character data, and the creation and maintenance of the underlying indexes
facilitating these queries.
Full-text indexes are contained in
full-text catalogs. Each database can contain one or more full-text catalogs.
A catalog cannot belong to multiple databases and each catalog can contain
full-text indexes for one or more tables. A table can only have one full-text
index, so each table with a full-text index belongs to only one full-text
catalog.
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Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
48
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||||||||||||
Heading:
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SQL Server
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||||||||||||
Question:
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What is the difference between Full text index and regular SQL
Indexes?
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||||||||||||
Answer:
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||||||||||||
Comments:
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|||||||||||||
Level:
|
SE/SSE
|
Number:
|
49
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Heading:
|
SQL Server
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Question:
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What is CONTAINS Predicate?
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Answer:
|
Is a
predicate used to search columns containing character-based data types for
precise or fuzzy (less precise) matches to single words and phrases, the
proximity of words within a certain distance of one another, or weighted
matches. CONTAINS can search for:
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Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
50
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Heading:
|
SQL Server
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Question:
|
What is FREETEXT Predicate?
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Answer:
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Is a predicate used to search columns
containing character-based data types for values that match the meaning and
not the exact wording of the words in the search condition. When FREETEXT is
used, the full-text query engine internally "word-breaks" the freetext_string
into a number of search terms and assigns each term a weight and then
finds the matches.
SELECT CategoryName
FROM Categories
WHERE FREETEXT (Description, 'sweetest candy bread and dry meat' )
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Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
51
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Heading:
|
SQL Server
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Question:
|
What are JOINS?
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Answer:
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Join
conditions can be specified in either the FROM or WHERE clauses; specifying
them in the FROM clause is recommended. WHERE and HAVING clauses can also
contain search conditions to further filter the rows selected by the join
conditions. Joins can be categorized as:
Inner joins use a comparison operator to match
rows from two tables based on the values in common columns from each table.
For example, retrieving all rows where the student identification number is
the same in both the students and courses tables.
Outer joins are specified with one of the
following sets of keywords when they are specified in the FROM clause:
The result set of a left outer join includes all
the rows from the left table specified in the LEFT OUTER clause, not just the
ones in which the joined columns match. When a row in the left table has no
matching rows in the right table, the associated result set row contains null
values for all select list columns coming from the right table.
A right outer join is the reverse of a left outer
join. All rows from the right table are returned. Null values are returned
for the left table any time a right table row has no matching row in the left
table.
A full outer join returns all rows in both the
left and right tables. Any time a row has no match in the other table, the
select list columns from the other table contain null values. When there is a
match between the tables, the entire result set row contains data values from
the base tables.
Cross joins return all rows from the
left table, each row from the left table is combined with all rows from the
right table. Cross joins are also called Cartesian products.
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Comments:
|
|
Level:
|
SE/SSE
|
Number:
|
52
|
Heading:
|
SQL Server
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Question:
|
Explain Precision, Scale and Length?
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Answer:
|
Precision is the number of digits in a number. Scale is the number of digits to the right of the decimal point in a number. For example, the number 123.45 has a precision of 5 and a scale of 2.
Length for a numeric data type is the number of bytes used to store the number. Length for a character string or Unicode data type is the number of characters. The length for binary, varbinary, and image data types is the number of bytes. For example, an int data type can hold 10 digits, is stored in 4 bytes, and does not accept decimal points. The int data type has a precision of 10, a length of 4, and a scale of 0.
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Comments:
|
|
Level:
|
SE/SSE
|
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