The ABS function returns the absolute value of a given number. The data type of the return value is the same as that of the argument.
ABS( number_operand )
--it returns the absolute value of the argument
SELECT ABS(12.3), ABS(-12.3), ABS(-12.3000), ABS(0.0);
abs(12.3) abs(-12.3) abs(-12.3000) abs(0.0)
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12.3 12.3 12.3000 .0