Mathematical Functions example,  ROUND(99.999, 2)  returns  100.00 —the first argument is  DECIMAL(5, 3) , and the return type is  DECIMAL(5, 2) . If the second argument is negative, the return type has scale 0 and a corresponding precision; ROUND(99.999, -1)  returns  100 , which is  DECIMAL(3, 0) . Returns the sign of the argument as  -1 ,  0 , or  1 , depending on whether  X  is negative, zero, or positive. Returns the sine of  X , where  X  is given in radians. Returns the square root of a nonnegative number  X . Returns the tangent of  X , where  X  is given in radians. Returns the number  X , truncated to  D  decimal places. If  D  is  0 , the result has no decimal point or fractional part.  D  can be negative to cause  D  digits left of the decimal point of the value  X  to become zero. mysql>  SELECT TRUNCATE(1.223,1); -> 1.2 mysql>  SELECT TRUNCATE(1.999,1); -> 1.9 mysql>  SELECT TRUNCATE(1.999,0); -> 1 mysql>  SELECT TRUNCATE(-1.999,1); -> -1.9 mysql>  SELECT TRUNCATE(122,-2); -> 100 mysql>  SELECT TRUNCATE(10.28*100,0); mysql>  SELECT TAN(PI()); -> -1.2246063538224e-16 mysql>  SELECT TAN(PI()+1); -> 1.5574077246549 mysql>  SELECT SQRT(4); -> 2 mysql>  SELECT SQRT(20); -> 4.4721359549996 mysql>  SELECT SQRT(-16); -> NULL mysql>  SELECT SIN(PI()); -> 1.2246063538224e-16 mysql>  SELECT ROUND(SIN(PI())); -> 0 mysql>  SELECT SIGN(-32); -> -1 mysql>  SELECT SIGN(0); -> 0 mysql>  SELECT SIGN(234); -> 1 • SIGN( X ) • SIN( X ) • SQRT( X ) • TAN( X ) • TRUNCATE( X , D ) 2149