Isempty

isempty checks if a value in a string column is an empty string ("").

In Metabase, you must combine isempty with another expression that accepts boolean values. The table below shows you examples of the boolean output that will be passed to your other expression(s).

How Metabase handles empty strings

In Metabase, columns with string data types will display blank cells for empty strings or null values (if the column is nullable in your database).

For example, in the column below, the empty cells could contain either:

• "": feedback was submitted and left intentionally blank, so the person had “no feedback to give”.
• null: no feedback was submitted, so the person’s thoughts are “unknown”.

Replacing empty strings with another value

Combine isempty with the case expression to replace empty strings with something more descriptive.

Let’s say that the second row’s blank cell is actually an empty string, so isempty will return true. The case statement evaluates true to return the first output “No feedback”.

The first row’s blank cell doesn’t have an empty string, but because it’s blank, we’re not sure what’s in it either—it could be a null, or even an emoji that blends into your table background. No matter what the edge case is, isempty will return false, and case will return whatever’s in the Feedback column as the default output.

Accepted data types

Limitations

• In Metabase, you must combine isempty with another expression that accepts boolean arguments (i.e., true or false).
• isempty only accepts one value at a time. If you need to deal with empty strings from multiple columns, you’ll need to use multiple isempty expressions with the case expression.
• If isempty doesn’t seem to do anything to your blank cells, you might have null values. Try the isnull expression instead.

Related functions

This section covers functions and formulas that can be used interchangeably with the Metabase isempty expression, with notes on how to choose the best option for your use case.

• SQL
• Spreadsheets
• Python

All examples below use the table from the Replacing empty strings example:

SQL

In most cases (unless you’re using a NoSQL database), questions created from the notebook editor are converted into SQL queries that run against your database or data warehouse.

CASE WHEN Feedback = "" THEN "No feedback"
     ELSE Feedback END

is equivalent to the Metabase isempty expression:

case(isempty([Feedback]), "No feedback.", [Feedback])

Spreadsheets

If our sample feedback column is in a spreadsheet where “Feedback” is in column A, then the formula

=IF(A2 = "", "Unknown feedback.", A2)

is equivalent to the Metabase isempty expression:

case(isempty([Feedback]), "No feedback.", [Feedback])

Python

Assuming the sample feedback column is in a dataframe column called df["Feedback"]:

df["Custom Column"] = np.where(df["Feedback"] == "", "No feedback.", df["Feedback"])

is equivalent to the Metabase isempty expression:

case(isempty([Feedback]), "No feedback.", [Feedback])

Further reading

• Custom expressions documentation
• Custom expressions tutorial