For a given number, it may be necessary to know the sign of the number for computation purposes.
If it is positive, zero or negative, you may have respective case to work on. The signs are returned as 1, 0, -1 for positive number, zero and negative number respectively.
Case 1: Positive number
SELECT SIGN(234) AS SIGN;where 234 is the value. +-------+| SIGN |+-------+| 1 |+-------+Case 2: Number is zero
SELECT SIGN(0) AS SIGN;where 0 is the value. +-------+| SIGN |+-------+| 0 |+-------+Case 3: Negative number
SELECT SIGN(-64500) AS SIGN;where -64500 is the value. +-------+| SIGN |+-------+| -1 |+-------+ 
