If the EDB data source supports creation of layers, there is the component type Layers among main EDB components. If this type is selected in a pane, then the menu command Edit+Add launches the EDB layer adding wizard; its first page is shown at the figure 41-4.
Figure 41-4. Wizard of adding EDB layer,step 1
On this page a name of the EDB layer being added and also parameters Base point and Range should be entered. The meaning of these two parameters is similar to the same parameters of a map (see chapter 9 “Map structure”, subsection “Creating a map”). It should be noted that for map's layers specification of base point and range is not provided, these parameters are common for the whole map. In contrast to that, EDB layers have no enveloping component similar to a map, so these parameters are to be specified for each layer separately. Besides, the parameter Partition is not provided for EDB layers.
On the same page, in the pane Link with records, there is a checkbox Create user key. The issues of linking spatial features with table records will be discussed later, in the chapter 43 “Links of maps with tables and queries of EDB”. Here it is enough to say that if the user checks this box then for each feature of the layer being created, data fields will be stored which can be used for setting links with tables. As a result of this, if the box is checked, next five pages of the layer adding wizard replicate pages of the EDB table adding wizard (see chapter 41 “Main EDB components”, subsection “Adding EDB table as a base table in data source”). These pages relate to creation of the table fields, its primary key, unique keys and indexes, and also allow manual modification of the generated SQL expression.
If the user key is not created, the wizard passes to the last page which contains the summary of the specified parameters of the layer. After pushing the button Execute the creation of the layer is performed.
The added EDB layer is originally empty, i.e. it does not contain any features or components. Later on the user can add feature types in the layer, as described in the chapter 9 “Map structure”, subsection “Adding map components”, perform browsing of the layer and all other operations which was described for map layers.
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