How To Delete Duplicates In Oracle

I'm testing something in Oracle and populated a table with some sample data, but in the process, I accidentally loaded duplicate records, so now I can't create a primary key using some of the columns. How can I delete all duplicate rows and leave only one of them? Let c how to remove duplicates from a table.I have one table here 'student' It has two duplicate records. 3 joe 4 robert These two records has duplicates. So I have to remove them.

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Problem Statement:
You want to find and remove duplicates from a table in Oracle.

Solution: We can use Oracle's internal ROWID value for uniquely identifying rows in a table. The sample syntax to acheive this would like below.

To demonstrate the usage, we will begin by creating sample data.

Example

Looking at the data we just created.

Example

So, we have inserted 3 duplciates which we wanted to remove. before we go on and write a Delete statement, let us understand the inner query with ROWID.

Example

I had intentionally added the columns player_rank and player_name to this innermost subquery to make the logic understandable. Ideally, innermost subquery could be written without them to the same effect. If we execute just this innermost query offcourse with the extra columns selected for clarity, we see these results.

The SQL returns the rowid for all the rows in the table. The ROW_NUMBER() function then works over sets of id and player_name driven by the PARTITION BY instruction. This means that for every unique player_rank and player_name, ROW_NUMBER will start a running count of rows we have aliased as rnk. When a new player_rank and player_name combination is observed, the rnk counter resets to 1.

Now we can apply the DELETE operator to remove the duplicate values as below.

SQL: Remove duplicates

Example

Output

DISTINCT is useful in certain circumstances, but it has drawback that it can increase load on the query engine to perform the sort (since it needs to compare the result set to itself to remove duplicates)

Below are alternate solutions :

1. Remove Duplicates Using Row_Number.

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Delete Duplicate Records In Sql

2.Remove Duplicates using self Join
YourTable

3. Remove Duplicates using group By
The idea is to group according to all columns to be selected in output. For example, if we wish to print unique values of 'FirstName, LastName and MobileNo', we can simply group by all three of these.

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Microsoft office 2010 product key hack. Please Improve this article if you find anything incorrect by clicking on the 'Improve Article' button below.

Solution: We can use Oracle's internal ROWID value for uniquely identifying rows in a table. The sample syntax to acheive this would like below.

To demonstrate the usage, we will begin by creating sample data.

Example

Looking at the data we just created.

Example

So, we have inserted 3 duplciates which we wanted to remove. before we go on and write a Delete statement, let us understand the inner query with ROWID.

Example

I had intentionally added the columns player_rank and player_name to this innermost subquery to make the logic understandable. Ideally, innermost subquery could be written without them to the same effect. If we execute just this innermost query offcourse with the extra columns selected for clarity, we see these results.

The SQL returns the rowid for all the rows in the table. The ROW_NUMBER() function then works over sets of id and player_name driven by the PARTITION BY instruction. This means that for every unique player_rank and player_name, ROW_NUMBER will start a running count of rows we have aliased as rnk. When a new player_rank and player_name combination is observed, the rnk counter resets to 1.

Now we can apply the DELETE operator to remove the duplicate values as below.

SQL: Remove duplicates

Example

Output

DISTINCT is useful in certain circumstances, but it has drawback that it can increase load on the query engine to perform the sort (since it needs to compare the result set to itself to remove duplicates)

Below are alternate solutions :

1. Remove Duplicates Using Row_Number.

Young jeezy albums youtube. Released in 2008. Artist: Young Jeezy Album: The Recession 2 Released: 2020 Style: Hip Hop Format: MP3 320Kbps Size: 113 Mb. Tracklist: 01 – Oh Lord 02 – Here We Go 03 – Modern Day 04 – Back 05 – Da Ghetto 06 – Niggaz 07 – Death Of Me 08 – Stimulus Check 09 – My Reputation 10 – The Glory 11 – Live And Die 12 – Praying Right 13 – Therapy. Download young.jeezy.the.recession.2.2020.rar fast and secure.

Delete Duplicate Records In Sql

2.Remove Duplicates using self Join
YourTable

3. Remove Duplicates using group By
The idea is to group according to all columns to be selected in output. For example, if we wish to print unique values of 'FirstName, LastName and MobileNo', we can simply group by all three of these.

Recommended Posts:

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Microsoft office 2010 product key hack. Please Improve this article if you find anything incorrect by clicking on the 'Improve Article' button below.

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