Where If

[Technocrat]

I have 3 fields that I need to match in two tables in MSSQL. Here is the layout:

Table 1:
StreetNumber
Street
FullAddress
Table 2:
StreetNumber
Street
MailAddress (its StreetNumber + Street)

Now for some stupid reason that I can only shake my head at in table 2 if the mailing address is the same as the street address, then the StreetNumber and Street are not populated. Also people might have the same mailing address for multiple address. So a simple OR is not working.

What I need is some like:

SELECT * FROM table1 WHERE (
If StreetNumber <> '' Then
table1.StreetNumber = table2.StreetNumber AND table1.Street = table2.Street
ELSE
table1.FullAddress = table2.MailAddress
END)

Any help?