Progress
Language Tutorial
for Windows
Defining Indexes
An index is a field or combination of fields from one table that Progress uses as the basis for searching, sorting, or otherwise processing the records of that table. As an example of index properties, access the property sheet for the Comments index of the Customer table as shown in Figure 4–6.
Figure 4–6: Index Properties Sheet
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An index is defined by several important properties. First, the index must have a unique name. If it is a simple index, based on one field, then name the index the same as the field component. If it is a compound index, based on several fields, give the index a descriptive name that describes the components of the index.
Next, the properties of an index include each component field and whether the component is ascending or descending. The selection list on the properties sheet lists the component fields and their ascending or descending status. When a field component is ascending, Progress sorts the index values from first to last (for example, A to Z or 1 to 10). When a field component is descending, Progress sorts the index values from last to first (for example, Z to A or 10 to 1). Note that you cannot change these properties after you create the index. Changing components or sort direction is equivalent to building a new index.
Finally, an index has a series of logical properties that define how the index works. These properties are represented as toggle boxes on the property sheet. Table 4–4 describes these properties.
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