DIFFERENCE (Transact-SQL)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
Analytics Platform System (PDW)
SQL analytics endpoint in Microsoft Fabric
Warehouse in Microsoft Fabric
This function returns an integer value measuring the difference between the SOUNDEX() values of two different character expressions.
Transact-SQL syntax conventions
Syntax
DIFFERENCE ( character_expression , character_expression )
Arguments
character_expression
An alphanumeric expression of character data. character_expression can be a constant, variable, or column.
Return Types
int
Remarks
DIFFERENCE compares two different SOUNDEX values, and returns an integer value. This value measures the degree that the SOUNDEX values match, on a scale of 0 to 4. A value of 0 indicates weak or no similarity between the SOUNDEX values; 4 indicates strongly similar, or even identically matching, SOUNDEX values.
DIFFERENCE and SOUNDEX have collation sensitivity.
Examples
The first part of this example compares the SOUNDEX values of two very similar strings. For a Latin1_General collation, DIFFERENCE returns a value of 4. The second part of the example compares the SOUNDEX values for two very different strings, and for a Latin1_General collation, DIFFERENCE returns a value of 0.
-- Returns a DIFFERENCE value of 4, the least possible difference.
SELECT SOUNDEX('Green'), SOUNDEX('Greene'), DIFFERENCE('Green','Greene');
GO
-- Returns a DIFFERENCE value of 0, the highest possible difference.
SELECT SOUNDEX('Blotchet-Halls'), SOUNDEX('Greene'), DIFFERENCE('Blotchet-Halls', 'Greene');
GO
Here's the result set.
----- ----- -----------
G650 G650 4
(1 row(s) affected)
----- ----- -----------
B432 G650 0
(1 row(s) affected)