A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can't contain Nulls.

soorajsk_84

 Profile Answers by soorajsk_84 Questions by soorajsk_84

• Aug 9th, 2007

A table can have any number unique keys but a single primary key

Thriveni P

• Mar 14th, 2006

A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can't contain Nulls.Unique key cannot be used to create referential integrity whereas primary key can do.

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UPDATE and DELETE Restrict - A referential integrity rule that disallows the update or deletion of referenced data.DELETE Cascade - When a referenced row is deleted all associated dependent rows are deleted.

bahwesh

• Jul 17th, 2007

Foreign key value must exist as PK value on?some other ?table...FK?value can be null but?PK can't

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Every ORACLE database has one or more physical data files. A database's data files contain all the database data. The data of logical database structures such as tables and indexes is physically stored in the data files allocated for a database.

sendhur

• Mar 15th, 2007

The data of logical database, say tables,indeses etc are stored in datafile.they can be associated with only one database. once created their size can not be altered. but we can add new data file to the table space.

Priya

• Sep 25th, 2006

Actually we can alter the size of the datafile by using the below syntaxSyntax :ALTER DATABASE DATAFILE RESIZE ;

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A segment is a set of extents allocated for a certain logical structure.

gaurav_varma

 Profile Answers by gaurav_varma Questions by gaurav_varma

• Jan 10th, 2007

A segment is a set of extents that contains all the data for a specific logical storage structure within a tablespace. For example, for each table, Oracle allocates one or more extents to form that ta...

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An Extent is a specific number of contiguous data blocks, obtained in a single allocation, and used to store a specific type of information.

gaurav_varma

 Profile Answers by gaurav_varma Questions by gaurav_varma

• Jan 10th, 2007

An extent is a logical unit of database storage space allocation made up of a number of contiguous data blocks. One or more extents in turn make up a segment. When the existing space in a segment is c...

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A synonym is an alias for a table, view, sequence or program unit.

thumatinagaraju

 Profile Answers by thumatinagaraju Questions by thumatinagaraju

• Oct 24th, 2006

Ya synonym is used to rename or to create alias for the data base object ..

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A sequence generates a serial list of unique numbers for numerical columns of a database's tables.

thumatinagaraju

 Profile Answers by thumatinagaraju Questions by thumatinagaraju

• Oct 24th, 2006

Nice answer soumyanag thumati_nagaraju@yahoo.co.in

soumya

• Jun 28th, 2006

A sequence is an automatically generated unique number.It is typically used to create a primary key value.It is a sharable object.Using sequence change the increment value, maximum value, minimum value, cycle option, or cache option.

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Views do not contain or store data.

sanjay Pramanaik

• Oct 5th, 2006

?Hi,?? It? depends on the type of view it is.? if it is a normal view than it does not contains the data. and if it is materialsed view than it contains the data.?Thanks sanjay pramanik

kehri_anurag

 Profile Answers by kehri_anurag Questions by kehri_anurag

• Jan 13th, 2006

No, View never contain the the data, Only defination of it stores in the data base, when ever you invoke them they show you the data based on their defination.Only Materlized view or SnaptShot contain the the data.

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Clusters are groups of one or more tables physically stores together to share common columns and are often used together.

partho sarathi konar

• Oct 1st, 2006

Clusters are groups of one or more tables physically stored together because they share common columns and are often used together. This improves disk access time.The related columns of the tables in ...

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A row is stored in a hash cluster based on the result of applying a hash function to the row's cluster key value. All rows with the same hash key value are stores together on disk.

partho sarathi konar

• Oct 1st, 2006

Hash Clusters cluster table data in a manner similar to normal, index clusters. To find or store a row in a hash cluster, Oracle applies a hash function to the row's cluster key value. The resulting h...

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Temporary segments are created by ORACLE when a SQL statement needs a temporary work area to complete execution. When the statement finishes execution, the temporary segment extents are released to the system for future use.

manish hoiyani

• Sep 14th, 2006

temporary segments are basically used for sort operations in oracle,,when the user tries to execute the query through order by clause. so system needs an space for an sort operation, and system   will use temporary segments  for this query.

manu

• Apr 7th, 2006

  To execute any program in Computer it needs memory area(RAM), Oracle allocates some memeory  for processing SQL statement. After execution this memory is released for future use. This one call Temporary work area.

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In Circumstances, all of the data for a row in a table may not be able to fit in the same data block. When this occurs , the data for the row is stored in a chain of data block (one or more) reserved for that segment.

feroz

• Aug 29th, 2006

If a row is too large to fit into a single database block row chaining happens. For example, if you use a 4KB blocksize for your database, and you need to insert a row of 8KB into it, Oracle will...

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If a foreign key reference a parent key of the same table is called self-referential integrity constraint.

samiksc

 Profile Answers by samiksc Questions by samiksc

• Jan 19th, 2006

Self referential integrity constraint refers to two columns related by referential integrity which belong to the same table.For example ManagerId column in employees table is a foreign key which refers to EmployeeId in the same table.

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A data block size is specified for each ORACLE database when the database is created. A database users and allocated free database space in ORACLE datablocks. Block size is specified in INIT.ORA file and can’t be changed latter.

Sumer

 Profile Answers by Sumer Questions by Sumer

• Jan 5th, 2006

stansard block size, which is set with parameter DB_BLOCK_SIZE cannot be changed after creating database. We can set non standard parameter size later with parameter DB_nk_BLOCK_SIZE and it can be changed.NOTE: Standard block size cnannot be equal to nonstandars block size.

NARENDER REDDY

• Jan 4th, 2006

It can be changed later also by setting block_size in init.ora like 2 or 4 or 8 or 16. this feature available from oracle 9i. it can support multi block size.

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