Here is an example SQL script with wrong outputs when UNOIN of MCS computes with DECIMAL with 38 digits precision when the precision is saturated.
An example wrong case is a UNION with DECIMAL(38) and DECIMAL(38,38). The result type in the system is a DECIMAL(38,38), which is wrong and can not represent any number with digits before the `.`.
The correct behaviour is to throw a warning when the precision of DECIMAL is saturated. However, there are some cases to be discussed.