Duplicate Elimination
Problem Description
SQL does not eliminate duplicates implicitly. It allows to enter duplicate values on columns other than candidate key or if did not specified any keys. If the user wants to eliminate duplicate records, he has to use DISTINCT keyword in the query.
Databases, therefore, can have duplicate entries. The problem deals with identifying and removing duplicates from a database.
Bounds Chart
Step Chart
Improvement Table
Complexity Classes  Algorithm Paper Links  Lower Bounds Paper Links 

Exp/Factorial  
Polynomial > 3  
Cubic  
Quadratic  [ Priority Queue Algorithm (1976)]  
nlogn  [Sorting based [Merge Sort] (1964)]
[Sorting based [Merge Sort] + realtime elimination (1964)] [BST Algorithm (1999)] [sorted neighborhood algorithm (1993)] [Duplicate elimination sorted neighborhood algorithm (DESNA) (2002)] 

Linear  
logn 