Top "Duplicates" questions

The "duplicates" tag concerns detecting and/or dealing with multiple instances of items in collections.

Delete duplicate rows from small table

I have a table in a PostgreSQL 8.3.8 database, which has no keys/constraints on it, and has multiple rows with …

sql postgresql duplicates
Linux command or script counting duplicated lines in a text file?

If I have a text file with the following conent red apple green apple green apple orange orange orange Is …

linux text duplicates
Pandas/Python: How to concatenate two dataframes without duplicates?

I'd like to concatenate two dataframes A, B to a new one without duplicate rows (if rows in B already …

python pandas duplicates
How to allow duplicate keys in php array

How to allow php array to have duplicate keys? When I try to insert a key, value pair with already …

php arrays duplicates
How to remove duplicates based on a key in Mongodb?

I have a collection in MongoDB where there are around (~3 million records). My sample record would look like, { "_id" = ObjectId("50731…

mongodb optimization duplicates key
JQuery: Remove duplicate elements?

Say I have a list of links with duplicate values as below: <a href="#">Book</a> &…

jquery duplicates
Filtering out duplicated/non-unique rows in data.table

Edit 2019: This question was asked prior to changes in data.table in November 2016, see the accepted answer below for both …

r duplicates data.table
Remove duplicate items from an array

I use the line of code below to loop through a table in my database: $items_thread = $connection -> …

php arrays duplicates array-unique
Delete duplicate items in Excel (including original value)

How to delete duplicate items in excelsheet(column), where it has to delete the items which has more than one …

excel duplicates excel-2007
Removing duplicate rows in vi?

I have a text file that contains a long list of entries (one on each line). Some of these are …

vim duplicates