IssueCertain file-based data sources in Tableau Desktop, such as Microsoft Access, Microsoft Excel, and text, may produce unexpected issues that are related to limitations with the Microsoft Jet database engine (Jet).
These issues can be difficult to troubleshoot, and most times the cause is not evident. Generally speaking there are two groups of issues:
- Issues that are related to data types, including errors in the data itself.
- Error messages that suggest that Tableau may have misinterpreted a field’s data type.
Symptoms of misinterpreted data types
After you establish the connection to your data from Tableau, you cannot force the connection to interpret a column differently. The data type definition must occur before the connection is established, in the underlying data.
Some specific symptoms that suggest misinterpreted data types include:
A field that should display as a dimension appears as a measure instead.
A field that should be a string, such as "ID," is interpreted as a numeric field (or vice versa).
Numbers are interpreted as dates, numbers are rounded incorrectly, etc.
Unexpected null values.
When creating a table join, you see the following error: Database error 0x80004005: Type mismatch in expression.
- Currency and other numeric values that are formatted for European locales can be misinterpreted. This can cause the following error: Microsoft JET database error 0x80004005: The text file specification field separator matches decimal separator or text delimiter.