The sign function oracle

Syntax size comparison function sign:
sign (n-)

Function:
the sign of the number n, greater than 0 return 1, -1 is less than 0, equal to 0 returns 0

示例：
1、select sign( 100 ),sign(- 100 ),sign( 0 ) from dual;

　　SIGN(100) SIGN(-100) SIGN(0)
　　———- ———- ———-
　　1 -1 0

2, a = 10, b = 20
　　then the sign (ab) -1