All About Oracle

Which command using Query Analyzer will give you the version of SQL server and operating

2008-05-10T14:56:00.004+05:30

Which command using Query Analyzer will give you the version of SQL server and operating
system?

Ans:

SELECT SERVERPROPERTY('productversion'), SERVERPROPERTY ('productlevel'), SERVERPROPERTY
('edition')

What is SQL server agent?

2008-05-10T14:56:00.003+05:30

SQL Server agent plays an important role in the day-to-day tasks of a database administrator (DBA). It
is often overlooked as one of the main tools for SQL Server management. Its purpose is to ease the
implementation of tasks for the DBA, with its full-function scheduling engine, 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

2008-05-10T14:56:00.001+05:30

Can a stored procedure call itself or recursive stored procedure? How many level SP nesting
possible?

Ans:

Yes. Because Transact-SQL supports recursion, you can write stored procedures that call themselves.
Recursion can be defined as a method of problem solving wherein the solution is arrived at by
repetitively applying it to subsets of the problem. A common application of recursive logic is to perform
numeric computations that lend themselves to repetitive evaluation by the same processing steps.
Stored procedures are nested when one stored procedure calls another or executes managed code by
referencing a CLR routine, type, or aggregate. You can nest stored procedures and managed code
references up to 32 levels.

What is @@ERROR?

2008-05-10T14:55:00.004+05:30

The @@ERROR automatic variable returns the error code of the last Transact-SQL statement. If there
was no error, @@ERROR returns zero. Because @@ERROR is reset after each Transact-SQL statement,
it must be saved to a variable if it is needed to process it further after checking it.

What is Raiseerror?

2008-05-10T14:55:00.003+05:30

Stored procedures report errors to client applications via the RAISERROR command. RAISERROR
doesn't change the flow of a procedure; it merely displays an error message, sets the @@ERROR
automatic variable, and optionally writes the message to the SQL Server error log and the NT
application event log.

What is log shipping?

2008-05-10T14:55:00.001+05:30

Log shipping is the process of automating the backup of database and transaction log files on a
production SQL server, and then restoring them onto a standby server. Enterprise Editions only
supports log shipping. In log shipping the transactional log file from one server is automatically updated
into the backup database on the other server. If one server fails, the other server will have the same db
can be used this as the Disaster Recovery plan. The key feature of log shipping is that is will
automatically backup transaction logs throughout the day and automatically restore them on the
standby server at defined interval.

What is the difference between a local and a global variable?

2008-05-10T14:54:00.004+05:30

A local temporary table exists only for the duration of a connection or, if defined inside a compound
statement, for the duration of the compound statement.
A global temporary table remains in the database permanently, but the rows exist only within a given
connection. When connection are closed, the data in the global temporary table disappears. However,
the table definition remains with the database for access when database is opened next time.

What command do we use to rename a db?

2008-05-10T14:54:00.003+05:30

sp_renamedb ‘oldname’ , ‘newname’
If someone is using db it will not accept sp_renmaedb. In that case first bring db to single user using
sp_dboptions. Use sp_renamedb to rename database. Use sp_dboptions to bring database to multi user
mode.

What is sp_configure commands and set commands?

2008-05-10T14:54:00.001+05:30

Use sp_configure to display or change server-level settings. To change database-level settings, use
ALTER DATABASE. To change settings that affect only the current user session, use the SET statement.

What are the different types of replication? Explain.

2008-05-10T14:53:00.002+05:30

The SQL Server 2000-supported replication types are as follows:
· Transactional
· Snapshot
· Merge
Snapshot replication distributes data exactly as it appears at a specific moment in time and does not
monitor for updates to the data. Snapshot replication is best used as a method for replicating data that
changes infrequently or where the most up-to-date values (low latency) are not a requirement. When
synchronization occurs, the entire snapshot is generated and sent to Subscribers.
Transactional replication, an initial snapshot of data is applied at Subscribers, and then when data
modifications are made at the Publisher, the individual transactions are captured and propagated to
Subscribers.
Merge replication is the process of distributing data from Publisher to Subscribers, allowing the
Publisher and Subscribers to make updates while connected or disconnected, and then merging the
updates between sites when they are connected.

What are the OS services that the SQL Server installation adds?

2008-05-10T14:53:00.001+05:30

MS SQL SERVER SERVICE, SQL AGENT SERVICE, DTC (Distribution transac co-ordinator)

What are three SQL keywords used to change or set someone’s permissions?

2008-05-10T14:52:00.002+05:30

GRANT, DENY, and REVOKE.

What does it mean to have quoted_identifier on? What are the implications of having it off?

2008-05-10T14:52:00.001+05:30

When SET QUOTED_IDENTIFIER is ON, identifiers can be delimited by double quotation marks, and
literals must be delimited by single quotation marks. When SET QUOTED_IDENTIFIER is OFF, identifiers
cannot be quoted and must follow all Transact-SQL rules for identifiers.

What is the STUFF function and how does it differ from the REPLACE function?

2008-05-10T14:51:00.004+05:30

STUFF function to overwrite existing characters. Using this syntax, STUFF(string_expression, start,
length, replacement_characters), string_expression is the string that will have characters substituted,
start is the starting position, length is the number of characters in the string that are substituted, and
replacement_characters are the new characters interjected into the string.
REPLACE function to replace existing characters of all occurance. Using this syntax
REPLACE(string_expression, search_string, replacement_string), where every incidence of
search_string found in the string_expression will be replaced with replacement_string.

Using query analyzer, name 3 ways to get an accurate count of the number of records in a

2008-05-10T14:51:00.003+05:30

Using query analyzer, name 3 ways to get an accurate count of the number of records in a
table?

ANS:

SELECT * FROM table1
SELECT COUNT(*) FROM table1
SELECT rows FROM sysindexes WHERE id = OBJECT_ID(table1) AND indid < 2

How to rebuild Master Database?

2008-05-10T14:51:00.001+05:30

Shutdown Microsoft SQL Server 2000, and then run Rebuildm.exe. This is located in the Program
Files\Microsoft SQL Server\80\Tools\Binn directory.
In the Rebuild Master dialog box, click Browse.
In the Browse for Folder dialog box, select the \Data folder on the SQL Server 2000 compact disc or in
the shared network directory from which SQL Server 2000 was installed, and then click OK.
Click Settings. In the Collation Settings dialog box, verify or change settings used for the master
database and all other databases.
Initially, the default collation settings are shown, but these may not match the collation selected during
setup. You can select the same settings used during setup or select new collation settings. When done,
click OK.
In the Rebuild Master dialog box, click Rebuild to start the process.
The Rebuild Master utility reinstalls the master database.
To continue, you may need to stop a server that is running.
Source: http://msdn2.microsoft.com/en-us/library/aa197950(SQL.80).aspx

What is the basic functions for master, msdb, model, tempdb databases?

2008-05-10T14:50:00.003+05:30

The Master database holds information for all databases located on the SQL Server instance and is the
glue that holds the engine together. Because SQL Server cannot start without a functioning master
database, you must administer this database with care.
The msdb database stores information regarding database backups, SQL Agent information, DTS
packages, SQL Server jobs, and some replication information such as for log shipping.
The tempdb holds temporary objects such as global and local temporary tables and stored procedures.
The model is essentially a template database used in the creation of any new user database created in
the instance.

What are primary keys and foreign keys?

2008-05-10T14:50:00.001+05:30

Primary keys are the unique identifiers for each row. They must contain unique values and cannot be
null. Due to their importance in relational databases, Primary keys are the most fundamental of all keys
and constraints. 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?

2008-05-10T14:49:00.000+05:30

Data integrity is an important feature in SQL Server. When used properly, it ensures that data is
accurate, correct, and valid. It also acts as a trap for otherwise undetectable bugs within applications.
A PRIMARY KEY constraint is a unique identifier for a row within a database table. Every table should
have a primary key constraint to uniquely identify each row and only one primary key constraint can be
created for each table. The primary key constraints are used to enforce entity integrity.
A UNIQUE constraint enforces the uniqueness of the values in a set of columns, so no duplicate values
are entered. The unique key constraints are used to enforce entity integrity as the primary key
constraints.
A FOREIGN KEY constraint prevents any actions that would destroy links between tables with the
corresponding data values. A foreign key in one table points to a primary key in another table. Foreign
keys prevent actions that would leave rows with foreign key values when there are no primary keys
with that value. The foreign key constraints are used to enforce referential integrity.
A CHECK constraint is used to limit the values that can be placed in a column. The check constraints
are used to enforce domain integrity.
A NOT NULL constraint enforces that the column will not accept null values. The not null constraints
are used to enforce domain integrity, as the check constraints.

What are the properties of the Relational tables?

2008-05-10T14:48:00.000+05:30

Relational tables have six properties:
· Values are atomic.
· Column values are of the same kind.
· Each row is unique.
· The sequence of columns is insignificant.
· The sequence of rows is insignificant.
· Each column must have a unique name.

What is De-normalization?

2008-04-18T16:38:00.001+05:30

De-normalization is the process of attempting to optimize the performance of a database by adding
redundant data. It is sometimes necessary because current DBMSs implement the relational model
poorly. A true relational DBMS would allow for a fully normalized database at the logical level, while
providing physical storage of data that is tuned for high performance. De-normalization is a technique
to move from higher to lower normal forms of database modeling in order to speed up database access.

How to get @@error and @@rowcount at the same time?

2008-04-18T16:37:00.005+05:30

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

What is Identity?

2008-04-18T16:37:00.003+05:30

Identity (or AutoNumber) is a column that automatically generates numeric values. A start and
increment value can be set, but most DBA leave these at 1. A GUID column also generates numbers,
the value of this cannot be controled. Identity/GUID columns do not need to be indexed.

What is a Scheduled Jobs or What is a Scheduled Tasks?

2008-04-18T16:37:00.001+05:30

Scheduled tasks let user automate processes that run on regular or predictable cycles. User can
schedule administrative tasks, such as cube processing, to run during times of slow business activity.
User can also determine the order in which tasks run by creating job steps within a SQL Server Agent
job. E.g. Back up database, Update Stats of Tables. Job steps give user control over flow of execution.

If one job fails, user can configure SQL Server Agent to continue to run the remaining tasks or to stop
execution.

What is a table called, if it does not have neither Cluster nor Non-cluster Index? What is it

2008-04-18T16:36:00.004+05:30

What is a table called, if it does not have neither Cluster nor Non-cluster Index? What is it
used for?

Ans:

Unindexed table or Heap. Microsoft Press Books and Book On Line (BOL) refers it as Heap.
A heap is a table that does not have a clustered index and, therefore, the pages are not linked by
pointers. The IAM pages are the only structures that link the pages in a table together.
Unindexed tables are good for fast storing of data. Many times it is better to drop all indexes from table
and than do bulk of inserts and to restore those indexes after that.

What is BCP? When does it used?

2008-04-18T16:36:00.003+05:30

BulkCopy is a tool used to copy huge amount of data from tables and views. BCP does not copy the
structures same as source to destination.

How do you load large data to the SQL server database?

2008-04-18T16:36:00.001+05:30

BulkCopy is a tool used to copy huge amount of data from tables. BULK INSERT command helps to
Imports a data file into a database table or view in a user-specified format.

Can we rewrite subqueries into simple select statements or with joins?

2008-04-18T16:35:00.006+05:30

Subqueries can often be re-written to use a standard outer join, resulting in faster performance. As we
may know, an outer join uses the plus sign (+) operator to tell the database to return all non-matching
rows with NULL values. Hence we combine the outer join with a NULL test in the WHERE clause to
reproduce the result set without using a sub-query

Can SQL Servers linked to other servers like Oracle?

2008-04-18T16:35:00.005+05:30

SQL Server can be lined to any server provided it has OLE-DB provider from Microsoft to allow a link.
E.g. Oracle has a OLE-DB provider for oracle that Microsoft provides to add it as linked server to SQL
Server group.

How to know which index a table is using?

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SELECT table_name,index_name FROM user_constraints

How to copy the tables, schema and views from one SQL server to another?

2008-04-18T16:35:00.001+05:30

Microsoft SQL Server 2000 Data Transformation Services (DTS) is a set of graphical tools and
programmable objects that lets user extract, transform, and consolidate data from disparate sources
into single or multiple destinations.

What is Self Join?

2008-04-18T16:34:00.004+05:30

This is a particular case when one table joins to itself, with one or two aliases to avoid confusion. A self
join can be of any type, as long as the joined tables are the same. A self join is rather unique in that it
involves a relationship with only one table. The common example is when company have a hierarchal
reporting structure whereby one member of staff reports to another.

What is Cross Join?

2008-04-18T16:34:00.003+05:30

A cross join that does not have a WHERE clause produces the Cartesian product of the tables involved
in the join. The size of a Cartesian product result set is the number of rows in the first table multiplied
by the number of rows in the second table. The common example is when company wants to combine
each product with a pricing table to analyze each product at each price.

Which virtual table does a trigger use?

2008-04-18T16:34:00.001+05:30

Inserted and Deleted.

List few advantages of Stored Procedure.

2008-04-18T16:33:00.004+05:30

· 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.

What is DataWarehousing?

2008-04-18T16:33:00.003+05:30

· Subject-oriented, meaning that the data in the database is organized so that all the data
elements relating to the same real-world event or object are linked together;
· Time-variant, meaning that the changes to the data in the database are tracked and recorded
so that reports can be produced showing changes over time;
· Non-volatile, meaning that data in the database is never over-written or deleted, once
committed, the data is static, read-only, but retained for future reporting;
· Integrated, meaning that the database contains data from most or all of an organization's
operational applications, and that this data is made consistent.

What is OLTP(OnLine Transaction Processing)?

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In OLTP - online transaction processing systems relational database design use the discipline of data
modeling and generally follow the Codd rules of data normalization in order to ensure absolute data
integrity. Using these rules complex information is broken down into its most simple structures (a table)
where all of the individual atomic level elements relate to each other and satisfy the normalization
rules.

How do SQL server 2000 and XML linked? Can XML be used to access data?

2008-04-18T16:32:00.001+05:30

How do SQL server 2000 and XML linked? Can XML be used to access data?
FOR XML (ROW, AUTO, EXPLICIT)

Ans:
You can execute SQL queries against existing relational databases to return results as XML rather than
standard rowsets. These queries can be executed directly or from within stored procedures. To retrieve
XML results, use the FOR XML clause of the SELECT statement and specify an XML mode of RAW, AUTO,
or EXPLICIT.

OPENXML

2008-04-18T16:31:00.001+05:30

OPENXML is a Transact-SQL keyword that provides a relational/rowset view over an in-memory XML
document. OPENXML is a rowset provider similar to a table or a view. OPENXML provides a way to
access XML data within the Transact-SQL context by transferring data from an XML document into the
relational tables. Thus, OPENXML allows you to manage an XML document and its interaction with the
relational environment.

What is an execution plan? When would you use it? How would you view the execution plan?

2008-04-18T16:30:00.000+05:30

An execution plan is basically a road map that graphically or textually shows the data retrieval methods
chosen by the SQL Server query optimizer for a stored procedure or ad-hoc query and is a very useful
tool for a developer to understand the performance characteristics of a query or stored procedure since
the plan is the one that SQL Server will place in its cache and use to execute the stored procedure or
query. From within Query Analyzer is an option called "Show Execution Plan" (located on the Query
drop-down menu). If this option is turned on it will display query execution plan in separate window
when query is ran again.

Global Temporary Tables

2008-04-07T21:12:00.001+05:30

I listened intently to the new Oracle programmer as he described all the struggles he's been having on his first big project. As I've done many times already in his short career, I interrupt with some words of wisdom.

"It's time to add Global Temporary Tables to your toolbelt."

"What are those?" he asks, as he opens the directory with the Oracle documentation. I smile. He has already learned where I always send him first.

"They're the ultimate work tables," I continue. "They're permanent tables, where you can add and modify session-specific data without affecting other sessions."

"What's so special about that?" he asks. "Even with regular tables, you can add and modify the data all you want without affecting other sessions. Just don't commit, and remember to rollback when your session is done."

"Oh yeah? And what about all the persistent work you're doing in your session? How do you commit that?"

"Oh yeah. Does it allow for indexes, and triggers, and views with regular tables?"

"Yep, all of that. See for yourself, it's easy. You've got the manual in front of you, so you drive."

Then I watched as he opened one session, and created a global temporary table.

SQL> CREATE GLOBAL TEMPORARY TABLE worktable (x NUMBER(3));

Table created.

He opened another session and was pleased to see the table there. He then added a row in the first session, committed it, and was planning to use the other session to see if the data was there. But instead he was in for a little surprise.

SQL> INSERT INTO worktable (x) VALUES (1);

1 row created.

SQL> SELECT * FROM worktable;

     X
----------
     1

SQL> commit;

Commit complete.

SQL> SELECT * FROM worktable;

no rows selected

"Hey!" he shouted. Heads popped up in nearby cubicles. "Where did it go?"

"Keep reading," I said, gesturing towards the "ON COMMIT" options for Global Temporary Tables. "By default, every time you commit your data, it is assumed that you want to clear out your work tables. Try PRESERVE."

He dropped the table, and tried again.

SQL> CREATE GLOBAL TEMPORARY TABLE worktable
2  (x NUMBER(3))
3  ON COMMIT PRESERVE ROWS;

Table created.

SQL> INSERT INTO worktable (x) VALUES (1);

1 row created.

SQL> SELECT * FROM worktable;

     X
----------
     1

SQL> commit;

Commit complete.

SQL> SELECT * FROM worktable;

     X
----------
     1

"That's better," he smiled. Now let's check the other session.

SQL> SELECT * FROM worktable;

no rows selected

"Excellent. So this data will remain there until my session ends?"

"Yep. Try it." He exited his session, logged back in, and sure enough the data was gone. "This is great. But what if I want to get rid of the data at some point in my session?"

"Truncate. Truncating the work table will only truncate the data in your session, not all the data."

"Hey neat. Thanks, this will be very useful. What are you doing for lunch later?"

"Aren't you even going to try it? What, you're just going to trust me?" I said. I think he was a little surprised that I would I'd rather talk about work tables than lunch. Frankly, so am I. Thankfully, he worked quickly, typing first in his second session.

SQL> INSERT INTO worktable (x) VALUES (2)

1 row created.

SQL> commit;

Commit complete.

SQL> SELECT * FROM worktable;

     X
----------
     2

SQL> TRUNCATE TABLE worktable;

Table truncated.

SQL> SELECT * FROM worktable;

no rows selected

SQL> commit;

Commit complete.

"I don't think you need all those commits," I laughed. "But ok, now look back in your first session. If the row you added previously isn't there, then I'm a big fat liar. Otherwise, we can talk about lunch."

SQL> SELECT * FROM worktable;

     X
----------
     1

"So how about sushi?" he asked.

"Sushi?" I groaned. "Haven't you learned anything from me?"