Oracle SQL: the Essential Reference

SOUNDEX

SOUNDEX(string)

Returns a string of digits representing phonetic pronunciation of the input string. The following steps are used to derive the output string:

1. The first letter of the string is retained.

2. All occurrences of the following letters are removed: a, e, h, i, o, u, w, and y.

3. Any remaining letters are replaced with digits as shown in Table 5-2.

4. The resulting string is truncated to four characters in length.

Using SOUNDEX can make it easier to search for a given string, because you don't need to spell it in exactly the correct way to get a match.

Table 5-2. SOUNDEX Letter-to-Digit Correspondence

Letters	SOUNDEX Digit
b, f, p, v	1
c, g, j, k, q, s, x, z	2
d, t	3
l	4
m, n	5
r	6

Example

SQL> SELECT SOUNDEX('O''Reilly'), SOUNDEX('ORiley'), SOUNDEX('OH Riley')
  2  FROM dual;

SOUN SOUN SOUN
---- ---- ----
O640 O640 O640