为什么在这种情况下PostgreSQL中没有“被零除”错误？

Question

Noticed the following behavior of PostgreSQL 9.5:

Division of something by zero - works as expected:

# select 1 / 0;
ERROR:  division by zero

Dividing NULL by zero:

# select NULL / 0;
 ?column?
----------

(1 row)

I browsed the documentation, but didn't find any reference to the reasons for such a design decision. The result of the dividend can depend on data - can be something or NULL , so the result - NULL or error - will depend on data. Wouldn't that be safer to throw error in all cases when divisor is known to be zero?

Answer 1

This is more about SQL Standard than anything:

An arithmetic operation involving a NULL returns NULL. For example, NULL minus NULL yields NULL, not zero.

The decision in this case is just to follow SQL ANSI.