MySQL 将 round() 中的小数限制为少于预期

Question

I have two different MySQL servers, when i run the following query on both, i get different results:

SELECT round(1/3,6) -- 0,333333 on Server1
SELECT round(1/3,6) -- 0,3333   on Server2

The first one gives 6 decimals as expected, the second one gives only 4 decimals.

SELECT format(round(1/3,6),6) -- 0,333333 on Server1
SELECT format(round(1/3,6),6) -- 0,333300 on Server2

SELECT round(cast(1 as float)/3,6) -- 0,333333 (6 decimals) on both

SELECT 1/3 -- 0,3333 (4 decimals) on both as expected

The MySQL Version is 8.0.18-9 on Server1 and 8.0.26-17 on Server2. div_precision_increment = 4 on both servers.

UPDATE:

Its a mysql version issue - when updated to 8.0.26 both servers have the same issue. But i think its the behaviour of 8.0.26 thats buggy.

In 8.0.27 there is a bugfix description that might address this issue:

Type resolution for negation did not set the proper precision when converting the type from integer to decimal. This is fixed by assigning the same precision as the argument. (Bug #32863037)

But Percona does not offer that update for now, so ill try to downgrade and then wait for 8.0.27+

Answer 1

UPDATE:

This is a error in the version, update the version of the 8.0.18 server to the same version

it is a server variable

SET div_precision_increment = 6;

will change for the session the number of digits. This variable indicates the number of digits by which to increase the scale of the result of division operations performed with the / operator. The default value is 4. The minimum and maximum values are 0 and 30, respectively. The following example illustrates the effect of increasing the default value.

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