SQL calculation for the sin() makes division by zero in one PosgreSQL function and don’t do it in another

There is a SQL call consisted of two general parts. The first one works, while the second one is commented out

select(2200 +
                        600 *
                                round(abs(sin(((1) * 0.042))) + 0.1) *
                                (sin(sin(((1) * 2 / 2 / 2.155172413793103 * PI()))) /
                                abs(sin(sin(((1) * 2 / 2 / 2.155172413793103* PI()))))) * --here is the division
                                (3 - exp(-12.5 + floor((1) * 2 / 2 / 2.155172413793103) * 2.155172413793103 * PI() * 2 * round(abs(sin(((1) * 0.042))) + 0.1) - (1 * 2 * PI())))
                        +
                        --600 *
                        --        abs(round(abs(sin(((1) * 0.042))) + 0.1) - 1) *
                        --        (sin(sin(((1) / 2 / 4.310344827586207 * PI()))) /
                        --        abs(sin(sin(((1) / 2 / 4.310344827586207 * PI()))))) * --here is the second division that causes the rpoblem
                        --        (3 - exp(-25.5 + floor((1) / 2 / 4.310344827586207) * 4.310344827586207 * PI() * 2 * abs(round(abs(sin(((1) * 0.042))) + 0.1) - 1) - (1 * PI())))
                        +50 * sin(3 + 1 * 0.092) + 350 * sin(3 + 1 * 0.012));

So, the question is why the

RROR:  division by zero
********** Error **********

ERROR: division by zero
SQL state: 22012

error occurs only if the second part is commented out. The part where the division occurs are all the same:

abs(sin(sin(((1) * 2 / 2 / 2.155172413793103 * PI()))))) *

vs

abs(sin(sin(((1) / 2 / 4.310344827586207 * PI()))))) *

they both should be zero, or none. But only the second one does throws the division by zero.

What is the root cause here and can I avoid that in the second state, is there a kind of type cas, or something else?

Answer

This is because there is difference in behaviour between integer division and float (decimal) division.

By following BODMAS rule:

Eg 1:

1. (1) * 2 / 2 / 2.155172413793103
2. 1 * 2 / 2 / 2.155172413793103
3. 1 * 1/2.155172413793103
4. 1 * 0.464
5. 0.464

Eg 2:

1. (1) / 2 / 4.310344827586207
2. 1 / 2 / 4.310344827586207
3. 0 / 4.310344827586207
4. 0

So, 1/2 = 0 (integer division) and 1/2.0 = 0.5 (float division)

Even after correcting this error, the expressions will return different results because of BODMAS priority order followed by machines (Brackets Of Division Multiplication Addition Subtraction).