Find duplicate records,delete duplicate records in sql,delete duplicate records in oracle,delete duplicate records in postgres,remove duplicates using sql. Query to find Duplicate Records in Table? Query to Delete Duplicate Records from table. Amit S October 29, 2017 7 Comments.

1. How To Remove Duplicates In Sql Query Using Rank
2. How To Eliminate Duplicates In Sql Query Pdf

It's easy to find duplicates with one field:

1. Finding duplicate values in a SQL table. Ask Question 1650. It's easy to find duplicates with one field: SELECT name, COUNT(email) FROM users GROUP BY email HAVING COUNT(email) 1 So if we have a table. Then we can use below query to delete duplicate query from table.
2. We some reason mistakely we had missed to add any constraints in SQL server table and the records has been inserted duplicate in all columns with front-end application. Then we can use below query to delete duplicate query from table.

So if we have a table

This query will give us John, Sam, Tom, Tom because they all have the same email.

However, what I want is to get duplicates with the same email and name.

That is, I want to get 'Tom', 'Tom'.

The reason I need this: I made a mistake, and allowed to insert duplicate name and email values. Now I need to remove/change the duplicates, so I need to find them first.

DineshDBAlexAlex

28 Answers

Simply group on both of the columns.

Note: the older ANSI standard is to have all non-aggregated columns in the GROUP BY but this has changed with the idea of 'functional dependency':

In relational database theory, a functional dependency is a constraint between two sets of attributes in a relation from a database. In other words, functional dependency is a constraint that describes the relationship between attributes in a relation.

Support is not consistent:

• Recent PostgreSQL supports it.
• SQL Server (as at SQL Server 2017) still requires all non-aggregated columns in the GROUP BY.
• MySQL is unpredictable and you need sql_mode=only_full_group_by:
  • GROUP BY lname ORDER BY showing wrong results;
  • Which is the least expensive aggregate function in the absence of ANY() (see comments in accepted answer).
• Oracle isn't mainstream enough (warning: humour, I don't know about Oracle).

Andriy Mgbngbn

try this:

OUTPUT:

if you want the IDs of the dups use this:

OUTPUT:

to delete the duplicates try:

OUTPUT:

simhumilecoKM.KM.Chris Van OpstalChris Van Opstal

If you want to delete the duplicates, here's a much simpler way to do it than having to find even/odd rows into a triple sub-select:

And so to delete:

Much more easier to read and understand IMHO

Note: The only issue is that you have to execute the request until there is no rows deleted, since you delete only 1 of each duplicate each time

AncAinuAncAinuMarthyMMoyed Ansari

A little late to the party but I found a really cool workaround to finding all duplicate IDs:

Tanmay NeheteTanmay Nehete

In case you work with Oracle, this way would be preferable:

This selects/deletes all duplicate records except one record from each group of duplicates. So, the delete leaves all unique records + one record from each group of the duplicates.

Select duplicates:

Delete duplicates:

Be aware of larger amounts of records, it can cause performance problems.

If you wish to see if there is any duplicate rows in your table, I used below Query:

How we can count the duplicated values??either it is repeated 2 times or greater than 2.just count them, not group wise.

as simple as

SysDragon

This is the easy thing I've come up with. It uses a common table expression (CTE) and a partition window (I think these features are in SQL 2008 and later).

This example finds all students with duplicate name and dob. The fields you want to check for duplication go in the OVER clause. You can include any other fields you want in the projection.

By Using CTE also we can find duplicate value like this

kapex

SELECT id, COUNT(id) FROM table1 GROUP BY id HAVING COUNT(id)>1;

I think this will work properly to search repeated values in a particular column.

Schemetrical

This should also work, maybe give it try.

Especially good in your case If you search for duplicates who have some kind of prefix or general change like e.g. new domain in mail. then you can use replace() at these columns

If you want to find duplicate data (by one or several criterias) and select the actual rows.

SELECT column_name,COUNT(*) FROM TABLE_NAME GROUP BY column1, HAVING COUNT(*) > 1;

To Check From duplicate Record in a table.

or

To Delete the duplicate record in a table.

or

We can use having here which work on aggregate functions as shown below

Here as two fields id_account and data are used with Count(*). So, it will give all the records which has more than one times same values in both columns.

How To Remove Duplicates In Sql Query Using Rank

We some reason mistakely we had missed to add any constraints in SQL server table and the records has been inserted duplicate in all columns with front-end application. Then we can use below query to delete duplicate query from table.

Here we have taken all the distinct records of the orignal table and deleted the records of original table. Again we inserted all the distinct values from new table to the original table and then deleted new table.

Suraj KumarSuraj Kumar

You can use the SELECT DISTINCT keyword to get rid of duplicates. You can also filter by name and get everyone with that name on a table.

adeshadesh

protected by Lalit Kumar BJul 22 '15 at 8:55

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