SUBSTR(x,a,b) is a string function that outputs part of the character string x (string specification of length n). Only expressions that have an alphanumeric value as a result are allowed as string specification x. LONG values are allowed. If x is a LONG value, you must specify length b of the desired subarea.

a and b are expressions. The value b may not be larger than the column definition for a CHAR column.

Result of the SUBSTR(x,a,b) Function


Part of the character string x that starts at the ath character and is b characters long.


SUBSTR(x,a,n-a+1) supplies all of the characters in the character string x from the ath character to the last (nth) character.

b is an unsigned integer


b can also have a value that is greater than (n-a+1).

b is not an unsigned integer


b must not be greater than (n-a+1).



As many blanks (code attribute ASCII, UNICODE) or binary zeros (code attribute BYTE) are appended to the end of this result as are needed to give the result the length b.

x, a, or b is a NULL value

NULL value


SQL Tutorial, Functions, Changing character strings