Avoid Data Duplication

If in a table we dont use primary key or any other unique key then how to avoid duplication of data?

Questions by maheshk_222

Showing Answers 1 - 9 of 9 Answers

You can create a unique index on the column/columns of a table.

A unique index can be created  as follows :

CREATE UNIQUE INDEX dept_unique_index ON dept (dname)

Here,  dept_unique_index is the name of the unique index.
dept  is the table name.
dname is the column on which the unique index will be created.


  • May 18th, 2010

You can use exists/not exists, but that unnecessary delays your insert command as every insert will be thoroughly checked, better apply unique constraint. PS: Additionally you can use distinct command to check for duplicacy.

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Ehsan Rehmani

  • Feb 1st, 2013

We must constraint the column with primary key when designing the database to avoid the duplications.

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Ehsan Rehmani

  • Apr 23rd, 2013

Its impossible to avoid duplication without constraint the PK on Column

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manohar reddy

  • Apr 4th, 2015

We can do it by validating the data before insertion in Trigger

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  • Apr 7th, 2015

It is possible by using unique constrain on that column we can avoid duplication of data

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  • Aug 6th, 2015

By creating unique index it is possible

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  • Aug 10th, 2015

Yes, by creating Unique index on the respective column we can avoid duplicate values into that particular column. But, with this NULL values can not be restricted.

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