select abs(1), abs(-1), abs(3.13), abs(-3.15), abs(1 - 2), abs(2 - 1), abs("1"), abs("-1");
abs(1)	abs(-1)	abs(3.13)	abs(-3.15)	abs(1 - 2)	abs(2 - 1)	abs("1")	abs("-1")
1	1	3.13	3.15	1	1	1	1