Oracle Notes (2)----substr use ____oracle

The use of Oracle's SUBSTR function
Gets the string substr (string, start_position, [length]) of the specified starting position and length in the string
Such as:
SUBSTR (' This are a test ', 6, 2) would return ' is '
SUBSTR (' This are a test ', 6) would return ' is a test '
substr (' techonthenet ', -3, 3) would return ' Net '
substr (' Techonthenet ',-6, 3) would return ' the '

Select substr (' Thisisatest ', -4, 2) value from dual result is TE

Select substr (' Emros ', -3,1) value from dual result is R

substr (' ABCDE ', -6) = null
substr (' ABCDE ', -5) = ' ABCDE '
substr (' ABCDE ', -4) = ' BCDE '
substr (' ABCDE ', -3) = ' CDE '
substr (' ABCDE ', -2) = ' de '
substr (' ABCDE ', -1) = ' E '
substr (' ABCDE ', -0) = ' ABCDE '