SQL: Structured Query Language - Oracle 10g Database Administration Concepts and Implementation Made Simple - page 26

This function allows you to compare words that are spelled
differently, but sound alike in English. You must have noticed
that if you do a search in google ( www.google.com ) using wrong
spelling e.g. as shown in the following figure, I made a wrong
spelled word “Neus” search on google and it came up with, “Did
you mean News?”. That is basically the beauty of this function.

Figure 2-7: Google website with “Did you mean” feature.

Example:

SELECT SUBSTR('SPIDERMAN',7,3) "Result"
FROM DUAL;
Output:

Result
---------
MAN

Similarly we can use SUBSTRB; for a single-byte database
character set, SUBSTRB is equivalent to SUBSTR. Floating-
point numbers passed as arguments to SUBSTRB are
automatically converted to integers. Assume a double-byte
database character set:

SELECT SUBSTRB(' SPIDERMAN',7,4.3) "Result"
FROM DUAL;