Need help interpreting mutiple IIF statement

[rbee]

Hello,



I've "inherited" someone else access DB and I need help to interpret this selection logic:

IIf(IsNull(a.[Lifecycle Stage 4 Sub-Stage]),IIf(IsNull(a.[Lifecycle Sub Stage 2]), a.[Lifecycle Stage], a.[Lifecycle Sub Stage 2]), a.[Lifecycle Stage 4 Sub-Stage]) AS [Sanitized Phase],

What I think it's saying:
If [Lifecycle Sub Stage 2] is null, use [Lifecycle stage], if [Lifecycle Sub Stage 2] is not null use [Lifecycle Sub Stage 2].
If [Lifecycle Stage 4 Sub-Stage] is not null, use [Lifecycle Stage 4 Sub-Stage].

I am not 100% sure if this is the correct interpretation as I have not had much previous experience interpreting multiple IIF statements in access. My aim is to migrate this process to Oracle, so I am just trying to get a handle around all the Access logic so that I can replicate the same behavior in another environment.

Any help with this would be much appreciated!

Thanks,
Raina.

[June7]

Starting from the left:

If [Lifecycle Stage 4 Sub-Stage] is null then do inner IIf else use [Lifecycle Stage 4 Sub-Stage]

An alternative structure is:

Nz([Lifecycle Stage 4 Sub-Stage], Nz([Lifecycle Sub Stage 2], [Lifecycle Stage]))

Nz() is an Access/VBA exclusive function.