Overview 

Testing cases where the integer value after truncating decimal operations differs from expectations

- Content: Test regarding differences in integer values after truncation that may occur when exceeding the decimal places 

- Environment: Tibero 7.2.2, 7.2.3 and above
  

Method

Decimal Rounding Policy in Tibero 

Supported decimal places and policies in Tibero 

Possible Cases

When the decimal part consists of repeating 9s and exceeds the decimal places 

• Numbers in the form XXX.XXXX999999... can differ as XXX.XXXX or XXX.XXX(X+1) depending on whether rounding up or truncation is applied.
• Since exceeding decimal places with continuous 9s requires operations with very large numbers, it is unlikely to occur in real environments.

--Case where rounding causes issues
Original value: 148950.999999999999999999999999999999999999999(9) 
Rounded: 148951.000000000000000000000000000000000000000

In this case, the integer part changes, causing an impact

--However, to create the above case by simple division:
999999999999999999999999999999
/1000000000000000000000000000000000000000

Requires such large-scale operations that it is unlikely to occur

Operations dividing and then multiplying by the same number 

• When dividing a number results in more than 38 decimal places, and then multiplying by the same number, issues may arise.
• Ideally, the original value should be returned, but rounding during the process can cause differences due to rounding up or down.
• If rounding up occurs at the last decimal place of the division result, the value becomes slightly larger; if rounding down, slightly smaller.
• Multiplying back the divided number results in a value between (X-1).99999....9999 and X.000000.....1, so truncating can yield either X-1 or X.

This can also occur with non-repeating decimals; for example, truncating 461730 may result in a value smaller by 1.

Conclusion

• It is difficult to assume that dividing and then multiplying by the same number will always return the identical number.
• Decimal places up to 38 are a very small range, so generally there is no impact.
• However, depending on the operation, differences may occur that change the integer part when truncating.