4.2: Projection Query

Next, we build a query that displays a subset of the columns of a table. Suppose we need to produce a listing of call numbers and titles. Proceed as in the previous example so that the Book table is shown in the Relationships area. Now, double-click the callNo and title fields:


Figure 4.9: Projection query with specific fields

The definition of the query is now complete. The grid area indicates the fields involved, and both fields will be displayed because each has a check mark on the Show line. Only fields checked on the Show line are displayed in the results. Running this query produces 2 columns:




Save the query. A projection query, because it displays a subset of the fields in the table, is said to produce a vertical slice of the table.


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