Returns a four-character soundex code for character strings that are composed of a contiguous sequence of valid single- or double-byte Roman letters.
soundex(char_expr | uchar_expr)
is a character-type column name, variable, or constant expression of char, varchar, nchar, or nvarchar type.
is a character-type column name, variable, or constant expression of unichar or univarchar type.
select soundex ("smith"), soundex ("smythe")
----- ----- S530 S530
soundex, a string function, returns a four-character soundex code for character strings that are composed of a contiguous sequence of valid single- or double-byte roman letters.
The soundex function converts an alphabetic string to a four-digit code for use in locating similar-sounding words or names. All vowels are ignored unless they constitute the first letter of the string.
If char_expr or uchar_expr is NULL, returns NULL.
ANSI SQL – Compliance level: Transact-SQL extension.
Any user can execute soundex.
Documentation Transact-SQL Users Guide
Function difference
