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From what I could understand :- Bridge tables are used when a dimension table can not be directly associated with a fact table.

e.g. In a bank's data warehouse a fact table of balance of a customer can't be stored with a customer ID as link between fact table and customer dimension due to the fact that multiple customers can be associated with same bank account. (i.e. joint account)

So fact table store account ID and bridge table between account dimension and customer dimension is used to distinguish.

But how are they different from helper tables which resolve many to many relationships between fact table and another dimension?

Tom V
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aarushi
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2 Answers2

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Bridge tables are the official name according to Dimensional Modeling as defined by the Kimball methodology.

Helper tables as far as I know have been used in many (often incorrect) contexts, one of which are bridge tables by people who fail to use the correct terminology.

Some people use helper table as a synonym for bridge tables, but helper tables also seem to have gotten misused in the context of a staging database or datawarehouses to name any table that helps something.

However, in dimensional modeling "helper table" isn't really defined, if it's used it's mostly as a synonym for "bridge table" (which is an actual term) or could be used to name about any table which "helps" achieving a goal but then there isn't a real definition.

Tom V
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From the definitions I've seen, helper tables and bridge tables are the same thing.

"A bridge table sits between a fact table and a dimension table and is used to resolve many-to-many relationships between a fact and a dimension. Bridge table will contain only two dimension column, key columns in both dimension."

see: http://dwhlaureate.blogspot.com/2012/10/bridge-table-in-datawarehouse.html

Nate
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