Databases Reference
In-Depth Information
7
ETL into a M
arket Basket Datamart
The purpose of the Market Basket Extract, Transform, and Load (ETL)
application is specifically to populate a Market Basket BI Table. If a Market
Basket application includes the Analysis branch shown in Figure 6.1,
then an ETL application populates data in a set of Market Basket tables
that are dedicated to the Analysis branch. If a Market Basket applica-
tion includes the Reporting branch shown in Figure 6.2, then an ETL
application populates data in a set of Market Basket tables that are dedi-
cated to the Reporting branch. For every set of Market Basket Analysis
tables, a set of ETL applications populates those tables. For every set of
Market Basket Reporting tables, a separate set of ETL applications popu-
lates those tables as well. The number of Market Basket ETL applications
equals the number of sets of Market Basket tables.
reQuIremeNt: PoPulAte the
mArket BAsket BI tABle
The first requirement of the Market Basket ETL is to extract data from
the data warehouse and load that data in the Market Basket BI Table. This
requirement may sound rather simple, but it is not. Although it may seem
that this requirement can be met by a SELECT statement that writes data
to an extract file, and then an INSERT statement that loads the data in the
extract file, an ETL application is not quite that simple. To avoid “garbage
out,” an ETL application must avoid “garbage in.” To avoid “garbage in,”
an ETL application must include safeguards to protect the data, and there-
fore the Market Basket application that will use the data.
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