The SUBSTRING and SUBSTR functions

You can use the SUBSTRING and SUBSTR functions to return a portion of a character string. You specify the start position and length (optional) to determine which portion of the character string the function returns.

Restriction: The units of measurement in the arguments to these two functions are bytes, rather than logical characters. This is of no importance in the default locale, nor in other single-byte locales, but you should not invoke SUBSTRING or SUBSTR in locales in which the logical characters of the code set can differ in their storage lengths.