Oracle's PL/SQL questions

Difference between post query and pre query?

silpa — Mon, 17 Sep 2007 17:59:57 +0000

post query will fire for every row that it fetched
pre query will fire only once

What is clustered index?

silpa — Mon, 17 Sep 2007 17:58:59 +0000

In clustered index rows are stored together based on clustered key values

What are referenced object?

silpa — Mon, 17 Sep 2007 17:58:05 +0000

copy of an object maintains link to the source object.
any changes to source object same are done reflected in the reference object

Steps involved in db shutdown?

silpa — Mon, 17 Sep 2007 17:56:44 +0000

shutdown the instance,dismount the db,close the db

Steps involved in db startup?

silpa — Mon, 17 Sep 2007 17:56:04 +0000

start an instance,mount the db,open the db

What is referential integrity?

silpa — Mon, 17 Sep 2007 17:55:26 +0000

A rule defined on a column (or set of columns) in one table that allows the insert or update of a row only if the value for the column or set of columns (the dependent value) matches a value in a column of a related table (the referenced value).

examples PK and FK

Types of db links?

silpa — Mon, 17 Sep 2007 17:54:23 +0000

Private
created on behalf of a specific user

Public
created for a special user group

Network
created and managed by network domain service.

Types of segments?

silpa — Mon, 17 Sep 2007 17:52:58 +0000

data segment
each non cluster/cluster table has a data segment.Tables data is stored in the extent of its data segment

index segment
each index has index segment to store its data

rollback segment
db contains one or more rollback segments to temporarily store undo information

temporary segment
temporary segments are created when SQL statements need temporary work area to complete execution.

Why use an index?

silpa — Mon, 17 Sep 2007 17:52:01 +0000

index gives faster access to data blocks in a table.

Difference between data block,extent and segment?

silpa — Mon, 17 Sep 2007 17:51:00 +0000

data block is the smallest unit of storage for a db object.
when objects grow they take additional storage of adjacent data blocks.These grouping of adjacent data blocks is called extent.
All the extents that an object takes when grouped together is called segment