Ok Imagine this scenario... now I am just inheriting this and not the original architect.... And my apologies for being generic but to show real data would make it even more confusing.
So say you have a table with 500 clients, but some are Diferent Branches
So say the 1st client is Acme SQL Servers (like that one? :))
Acme SQL Servers is in Field A
In Field B there are East, West, Central
In Field C there are North East, North West, South East, SouthWest, East Central, West Central
So it looks like this
Acme SQL Servers East North East
Acme SQL Servers East South East
Acme Computers East
Acme Computers West
Acme Hard Drives East North West
And you have a sales table that you want to join it with
Now here is where it gets interesting:
Inserting a key in the sales data is not an option.
There are some fields in the sales table that will allow you to extrapulate who the client was but this is what is requiring the cases...
If a certain code has data in Field A,B & C then we need to join on a certain field
If there is no data in c but there is in A & B then we would join on a different field
If there is no data in b & c but there is in A then we would join on a different field
The only way I could think of doing it (but dont laugh here, it seems to work) is:
Select all the data where field C is not null
Select all the data where field c is null but field a & b are not null
Select all the data where field B & C Are null but not A
This is a very taxing pull on the server because we are talking about returning anywhere from 1-8 million records.