Errors in software suck. Who hasn’t spent time crying into their keyboard or banging their head against their screen asking the computer gods to solve their problems? Agreed—no one! As I have used Prep Builder a lot, I have developed a good sense of the common mistakes people make with the tool. This chapter will address the following trouble spots and pose some potential solutions:
Parameter errors
Blank Profile and Data panes
Errors within a Calculated Field
You may often see an error message including the word parameters. For example, the error message in Figure 41-1 reads Function 'DATEADD' can't accept parameters: (string, integer, string)
.
In this case, parameters are the data fields, numbers, and strings you are entering into your calculations. The calculation expects a certain data type in these fields and can’t accept a different one. In this specific case, my colleague was using a date in a string field. The DATEADD()
function specifically needs a valid date for the calculation to increment.
Be sure to check the data types that you are using in the calculation against what the syntax expects. Remember, you can see an example of each function’s syntax to the right of the Reference list in the Edit Field dialog.
There are multiple causes for blank Profile or Data panes, but I’ve found a few common culprits.
In Figure 41-2 I have created a duplicate NPS field, but I removed the original field in an earlier step.
Obviously, this breaks the flow, but I’ve done it to show the source of the issue. In Figure 41-3, the red exclamation point above the duplicate NPS field shows where the error prevents the flow from running, but this isn’t where you would actually fix the flow; you need to do that in the earlier step where the original field was removed.
Use the Changes pane in Prep to work your way back through the flow to find where that original field was deleted. The error icon in the top-right corner of your flow allows you to read the error description, but the “View in flow” option in the bottom corner of this dialog box takes you to the error (Figure 41-4).
There’s no easy solution here, but at least this might help you find where to start working your way backward.
When you are using any data tool, if you change the data source in any way other than adding more rows of data, you are likely to get errors. Prep Builder is no exception. Common changes to check for are:
The data source being used has been moved.
The data source has been deleted.
The columns used in calculations have been removed.
The columns used in calculations have been renamed.
All of these changes will likely result in Prep Builder returning a blank Profile pane, as no data load will be possible, or data fields will appear in the Clean step with only null or blank values (Figure 41-5).
When errors occur in Prep Builder, they may not be as catastrophic as losing all of your data as in the case just shown. Calculated Field errors are the most common mistakes you will make, but generally they are very easy to fix when you know how to spot them.
When writing calculations, you will very quickly see when the calculation is not in the format that Prep Builder is expecting. For example, the calculation in Figure 41-6 is erroring because the IF
statement does not have an END
condition yet.
By clicking the “1 error” arrow at the bottom of the Calculation Editor, you can quickly see what is missing in your calculation. When building IF
statements, I often add the END
condition early and then edit the calculation between the words IF
and END
so I can see when each condition is complete as the error disappears (Figure 41-7).
If you have worked with other data software before, sometimes you find yourself using tried-and-tested methods elsewhere. This is especially true for Tableau Desktop users who use Prep Builder. Using functions that are supported elsewhere but unsupported by Prep Builder—either in a certain area or altogether—can cause you a lot of frustration, even for simple functions like sum()
, as shown in Figure 41-8.
To resolve this error, you would need to use either an Aggregate step or a Level of Detail (LOD) calculation, as these are the areas where Prep Builder does support calculating totals.
Errors occurring in software when you least expect them can be very frustrating. The time you spend decoding them is time lost from the analysis and production of other pieces of work. Blank Data panes are a sign that something is amiss within Prep, and the warning symbols can get you only so far, but hopefully this chapter has given you a starting point to approach these challenges.