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himanshu karki
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Oracle Object Type
Object Types Oracle implements Objects through the use of TYPEs, defined in a similar way to packages. Unlike packages where the instance of the package is limited to the current session, an instance of an object type can be stored in the database for later...

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Choosing a Primary Key: Natural or Surrogate?
This post overviews strategies for assigning primary keys to a table within a relational database. In particular, it focuses on the issue of when to use natural keys and when to use surrogate keys. Some people will tell you that you should always use natura...

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Key Differences Between DBMS and RDBMS
A database is a collection of data that is stored in an organized manner. This data can either be on a computer or on paper. It is, of course,   more efficient to store data on a computer , as the computerization of this data makes it easy to retrieve and p...

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Snowflake and Star Schemas in Data Warehousing
Schema is a logical description of the entire database. It includes the name and description of records of all record types including all associated data-items and aggregates. Much like a database, a data warehouse also requires to maintain a schema. A data...

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Introduction to Database Design
This article/tutorial will teach the basis of relational database design and explains how to make a good database design. It is a rather long text, but we advise to read all of it. Designing a database is in fact fairly easy, but there are a few rules to st...

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Oracle MERGE statement - Features, Enhancements and Logging
The  MERGE  statement was introduced in Oracle 9i to conditionally insert or update data depending on its presence, a process also known as an "upsert". The  MERGE  statement reduces table scans and can perform the operation in parallel if required.  With d...

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Data Warehousing
Data Warehouse Definition Different people have different definitions for a data warehouse. The most popular definition came from Bill Inmon, who provided the following: A data warehouse is a subject-oriented, integrated, time-variant and non-volatile colle...

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Oracle Flashback Query (SELECT AS OF)
To use Oracle Flashback Query, use a  SELECT  statement with an  AS   OF  clause. Oracle Flashback Query retrieves data as it existed at an earlier time. The query explicitly references a past time through a time stamp or System Change Number (SCN). It retu...

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Oracle Optimizer's Join Method
A join method is the mechanism for joining two row sources. Depending on the statistics, the optimizer chooses the method with the lowest estimated cost. This section contains the following topics: Nested Loops Joins Hash Joins Sort Merge Joins Cluster Join...
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