Soundex is an intresting and admiring function which will compare string pronounciations but not the actual strings.

In simple words a function to compare phonetics rather than letters/characters.

The function indeed uses soundex aligorthm

This may also be an aligorthm used for spelling suggestions in some places.

For example google shows proper word in Did you mean

Now to be more clear let me explain with an example for you.
In english the word ball and boll both are pronounced similarly although their spellings are different
if we use = operator in mysql as below it will give 0 (zero) as they are not same
select 'ball'=soundex('boll') from dual
But, if we use the function soundex as below it will give 1 as both are pronounced similar.
select soundex('ball')=soundex('boll') from dual
On the other hand sometimes when we have to do a select with where check then we can use sounds like
Sample select with where statement is
select * from toys where toy_name sounds like 'boll'
Sample statement result is(assume toys table has some records)

Try urself with some words listed below
  • principle,principal,princpl
  • text,test
  • next,nest
  • tool,tuul
  • tie,tih