请求排查以下iif表达式代码的错误：iif([INLotSerialStatus.LotSerialNbr]=NULL,...)

Hey there, let's break down the problems in your IIF expression and get it fixed:

First, let's list out the key problems with your current code:

• Wrong way to check for NULL
  In almost all database/expression languages, you can't use = NULL to test if a value is null. Null represents an unknown value, so any equality comparison with it won't work as expected. You need to use IS NULL instead.

• Mismatched parentheses & syntax mistakes
  Your expression has bracket issues that will make it fail to run:

  1. The Left() function is missing a closing parenthesis. You have Left([INLotSerialStatus.LotSerialNbr], InStr([INLotSerialStatus.LotSerialNbr], '*') but need to add a ) at the end of that call.
  2. There's an extra opening parenthesis before Left() that shouldn't be there, and the entire IIF function is missing a final closing parenthesis to wrap up all arguments.

• Logical error with null handling
  If [INLotSerialStatus.LotSerialNbr] is null, trying to run Left() or InStr() on it will throw an error—you can't perform string operations on a null value. It looks like you probably flipped your logic: you likely want to run the substring operation when the value isn't null, and return 'False' when it is null.

Here's a fixed version that aligns with what I assume your intended logic is (return the part of the string before the first '*' when the value exists, else return 'False'):

IIf([INLotSerialStatus.LotSerialNbr] IS NOT NULL, Left([INLotSerialStatus.LotSerialNbr], InStr([INLotSerialStatus.LotSerialNbr], '*') - 1), 'False')

A quick note: I added -1 to the InStr() result because without it, your substring would include the '' character itself. Feel free to remove that if your original goal was to include the '' in the output.

内容的提问来源于stack exchange，提问作者Japsidoo