Syntax
SUBSTR({ CharacterExpression },
StartPosition [, LengthOfString ] )
The parameter startPosition and
the optional parameter lengthOfString are both integer expressions.
The first character or bit has a startPosition of 1. If you specify
0, Derby assumes that you
mean 1.
The parameter characterExpression is a CHAR, VARCHAR,
or LONG VARCHAR data type or any built-in type that is implicitly converted
to a string (except a bit expression).
For character expressions, the startPosition and lengthOfString parameters
refer to characters. For bit expressions, the startPosition and lengthOfString parameters
refer to bits.
If the startPosition is positive, it refers to
position from the start of the source expression (counting the first character
as 1). The startPosition cannot be a negative number.
If the lengthOfString is
not specified, SUBSTR returns the substring of the expression from the startPosition to
the end of the source expression. If lengthOfString is specified, SUBSTR
returns a VARCHAR or VARBIT of length lengthOfString starting at the startPosition.
The SUBSTR function returns an error if you specify a negative number for
the parameter lengthOfString.
Examples
To return a substring of the word
hello,
starting at the second character and continuing until the end of the word,
use the following clause:
VALUES SUBSTR('hello', 2)
The
result is '
ello'.
To return a substring of the word
hello,
starting at the first character and continuing for two characters, use the
following clause:
VALUES SUBSTR('hello',1,2)
The result
is '
he'.
