Problem merging on decimal data type

[BrunieToons]

Does anyone know why about 10% of my records fail to join on this ID column, which is comes in from the data source as a decimal format? When I transform it to int, the join works. Here is the merge preview when both columns are in decimal format:

[edhans · Accepted solution]

Change it to integer format first. Decimal has 15 level precision and since PCs are floating point, what looks like to you 3 might be 2.9999999999999 or 3.000000001. You've seen that in Excel.

merging on whole numbers will work fine.