When you plan
to join data sources (tables or queries), the order in which you add
the data sources to the workspace matters. The first data source that
is added to the workspace is automatically assigned as the left table
for any joins that you add to the query.
If you are designing
a query that uses a fact table and dimension tables, drag and drop
the fact table onto the workspace first. You can perform left, right,
or full joins with the dimension tables faster because you need to
specify the join type only. However, if you drag and drop a dimension
table first, you can easily use the
button on the
Joins tab
to switch the left and right tables in the join.
If you are not using
a fact table or dimension tables, then the sequence for adding tables
to the workspace might not be very important. Just remember that the
first table dropped onto the workspace is assigned as the left table,
and you can switch the left table and right table on the
Joins tab.SAS Visual Data Builder
takes advantage of vendor-specific features in SQL processing whenever
possible. If the source tables are from a third-party vendor database,
the
SAS/ACCESS Interface engine can optimize the performance of the
query by passing the SQL statements through to the database.