Using nested IIF expressions in an update query - is it possible?

Question

Hi everyone,
I've been tasked by my manager to build a database which replicates a large, complicated Excel spreadsheet that consumes too much of our team's time and system resources. I've just about got most of it, but there is one particular required field that, in
Excel, requires multi-layered nested If/Then formulae. I have to ask if building something similar in Access is possible. Here is the problem and the logic:
Let us assume two established fields, Field 1 and Field 2; and then one field to be created via Update query, Field 3.
Let us further assume that in Fields 1 and 2, there are three specific alphanumeric sequences occurring (“X1A”, “X1”, and “Z1”) that need to be identified and then called out as either “S1” or “U1” in field 3.
If an Update Query were to be written to populate Field 3 with either “S1” or “U1” depending on one of the three alphanumeric sequences appearing in either Field 1 or Field 2, could it be written as the following expression, using the IIF and OR operators?
And if so, is the syntax of the following expression correct?
IIf([FIELD 1]="* X1A", "U1", OR IIf([FIELD 2]="* X1", "U1", OR IIf([FIELD 2]="* Z1", "U1", OR IIf([FIELD 1]="* X1", "U1", OR IIf([FIELD 1]="* Z1", "U1", "S1")))))
Any help, critiques, or guidance would be appreciated.

Answer 1

IMHO, a main consideration when "migrating" from Excel to Access is that a relational database is fundamentally different from a spreadsheet (although there can be much overlap).  In Excel, calculated values are "live" (unless you paste the values only
into some other cells).  To replicate this "live" quality in Access, you can use a query with a calculation to display (not create or update) Field 3 in your case; Field 3 really wouldn't be a field, just a representation (query, form, report) or snapshot
(export, print).  One reason for this is to avoid conflicts and redundancy.  In other words, if Field 3 is based solely on Fields 1 & 2 and some rule, then usually there is no need to waste disk space to store Field 3 and you don't risk Field
3 being wrong as in the case when the rule changes.
So here are a couple of options.
1) Create view only query to display Field 3.  In query design view, enter the following where you would normally select a field:
[FIELD 3]: IIf([FIELD 1]="* X1A", "U1", IIf([FIELD 2]="* X1", "U1", IIf([FIELD 2]="* Z1", "U1", IIf([FIELD 1]="* X1", "U1", IIf([FIELD 1]="* Z1", "U1", "S1")))))
I assume you literally mean the asterisk character and are not trying to invoke a wildcard for the LIKE operator.
There are other ways of doing this (e.g. with the LIKE operator or multiple queries and UNION), but I leave that up to you to explore.
2) Actually update the value of FIELD 3 in a table.  Create two update queries and use your rules as conditions (i.e. the criteria in the bottom of query design).
a) Update query 1 (run first): set [FIELD 3] = "U1" where [FIELD 1] = "* X1A" OR [FIELD 1] = "* X1" OR [FIELD 1] = "* Z1" OR [FIELD 2] = "* X1" OR [FIELD 2] = "* Z1"
b) Update query 2 (run after): set [FIELD 3] = "S1" where [FIELD 3] is null
Again, there are other ways of doing this such as setting the default value of [FIELD 3] in the table to "S1" and just running update query 1.
Good luck.