Expression to identify the row or rows on which to perform the transform. Expression must evaluate to true or false.

Examples:

ExpressionDescription
Score >= 50
true if the value in the Score column is greater than 50.
LEN(LastName) > 8
true if the length of the value in the LastName column is greater than 8.
ISMISSING([Title])
true if the row value in the Title column is missing.
ISMISMATCHED(Score,['Integer'])
true if the row value in the Score column is mismatched against the Integer data type.