Question

Here’s an example of Soundex code in SQL:

SELECT SOUNDEX('Smith'), SOUNDEX('Smythe');
----- ----- 
S530  S530  

How does 'Smith' become S530?

In this example, the first digit is S because that’s the first character in the input expression, but how are the remaining three digits are calculated?

Answer 1

Take a look a this article

The first letter of the code corresponds to the first letter of the
name. The remainder of the code consists of three digits derived from
the syllables of the word according to the following code:

• 1 = B, F, P, V
• 2 = C, G, J, K, Q, S, X, Z
• 3 = D, T
• 4 = L
• 5 = M,N
• 6 = R

The double letters with the same Soundex code, A, E, I, O, U, H, W, Y,
and some prefixes are being disregarded…

So for Smith and Smythe the code is created like this:

S  S   ->   S
m  m   ->   5
i  y   ->   0
t  t   ->   3
h  h   ->   0
   e   ->   -