Microsoft Excel (.xlsx) and Comma-Separated Values (.csv) Types

This section is written to differentiate between Excel and CSV files and discuss how they are connected to Tableau. Because of their simplicity and familiarity with users, these are the most likely files used to connect to Tableau.

Excel is a specialist spreadsheet format from Microsoft that has been popular for data storage for decades.The comma-separated values (CSV) file is named as such because values within it are distinguished (delimited) by commas. Each line in the file constitutes a distinct record. The CSV format is generic and not associated with a particular software or service, though files are often opened and used with Microsoft Excel or Google Sheets.

The plain-text format of CSVs is simple to create and straightforward for programs to read, making it easier to move data between systems or locations without complicated parsing steps. CSV files appear no different from spreadsheets when opened in Excel or Tableau – almost all software designed for use with data automatically displays the mass of comma-delimited text in a tabular structure of columns and rows.

As both file types are commonplace, there is a low barrier to entry – the formats are familiar to a wide range of computer users. However, as with most files, these types offer a snapshot of data in time; they are not automatically updated in the way that connections to live source systems are.

Note that CSV files typically cast values as plain text, even when all values are in a specific format – fields that are fully numerical, for example, may still be returned as strings. When first opened in Tableau Desktop, fields often need converting to appropriate data types such as String, Integer, or Float, so that there will be no errors when building calculations. Excel files have a hard limit of approximately one million records, determined by the maximum memory available in the Microsoft Excel software itself; note that this also applies to imported CSVs.