Implementations of Dice's Coefficient used to get a similarity index between two strings.

Dice.cs

public static double DiceCoefficient(string stOne, string stTwo)
{
	HashSet<string> nx = BuildBigramSet(stOne);
	HashSet<string> ny = BuildBigramSet(stTwo);

	HashSet<string> intersection = new HashSet<string>(nx);
	intersection.IntersectWith(ny);

	double dbOne = intersection.Count;
	return (2 * dbOne) / (nx.Count + ny.Count);

}
		
public static HashSet<string> BuildBigramSet(string input) 
{
	HashSet<string> bigrams = new HashSet<string>();
	
	for (int i=0; i < input.Length - 1; i++) 
	{
		bigrams.Add(input.Substring(i, 2));
	}
	return bigrams;
}

dice.py

def build_bigram_set(input_str):
    bigrams = set()
    
    for i in range(len(input_str)):
        bigrams.add(input_str[i:i+2])
        
    return bigrams

def dice_coefficient(lhs, rhs):
    lhs_bigrams = build_bigram_set(lhs)
    rhs_bigrams = build_bigram_set(rhs)
    
    intersection = lhs_bigrams & rhs_bigrams
    intersection_count = len(intersection)
    total_count = len(lhs_bigrams) + len(rhs_bigrams)
    
    return (2 * intersection_count) / total_count

Dice.sql

CREATE FUNCTION [ETL].[DiceCoefficient]
(
	@strOne nvarchar(2048), 
	@strTwo nvarchar(2048)
)
RETURNS FLOAT
AS
BEGIN
	declare @set1 table (bigram nchar(2) not null);
	declare @set2 table (bigram nchar(2) not null);
	declare @intersection table (bigram nchar(2) not null);

	declare @i int = 1;
	while (@i < LEN(@strOne))
	begin
		insert @set1 
		values (lower(SUBSTRING(@strOne, @i, 2)))
		set @i = @i + 1;
	end

	set @i = 1;

	while (@i < LEN(@strTwo))
	begin
		insert @set2
		values (lower(SUBSTRING(@strTwo, @i, 2)))
		set @i = @i + 1;
	end

	insert @intersection
	select distinct bigram
	from @set1
	intersect 
	select distinct bigram 
	from @set2


	declare @result float = (select (2.00 * (select cast(COUNT(*) as float) from @intersection)) /
		((select cast(COUNT(*) as float) from @set1) + (select cast(COUNT(*) as float) from @set2)))

	RETURN @result
END