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AVS stores the street number suffix in a char(1) - therefore the change notification messaging has a bug.
This is potentially a difficult issue because a number legacy systems and reports rely on this char(1) field.
http://sfgovdt.jira.com/browse/MAD-122
Unit
Let's go right to an example.
"100 Main St. Apartment A"
In this example "Apartment" is the unit type and "A" is the Unit Number.
Other examples include:
"100 Main St. Suite 100"
"100 Main St. Basement"
"100 Main St. #3"
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