The set of properties for a field of EDB query does not depend on whether the present query was built by constructive method or by specifying SQL statement SELECT directly. This set combines a set of field properties inherited from the component of the data source (similar to field properties of EDB table) and a set of properties characterising usage of field in ObjectLand (field width, computing operations, usage of reference table, etc.).
At figure 42-10 the page “General” of the property sheet of EDB query is shown.
Figure 42-10. Property sheet “Properties of field” for EDB query, page “General”
In table 42-2 field properties for EDB query displayed on page “General” are enumerated and explained.
Column | Description |
Field | Name of field of EDB query |
Table | Name of component of data source to which the field belongs on the basis of which the query field is determined. |
Field in table | Name of that field in component of the data source on the basis of which the query field is determined. |
Table owner | Name of the owner of the data source component to which the field belongs on the basis of which the query field is determined. If the source does not support the notion of an owner, an empty string is displayed. |
Type | Type of field of component of the data source on the basis of which the query field is determined. Displayed names of field types are specific for a particular source. |
Precision | Size of field of component of the data source on the basis of which the query field is determined. See parameter for a field of EDB table with the same name, table 42-1. |
Scale | Scale of field of component of the data source on the basis of which the query field is determined. See parameter for a field of EDB table with the same name, table 42-1. |
Reference table | Name of reference table set for a field. If no reference table is used for the field, an empty string is displayed. |
Reference owner | Name of owner of the reference table set for a field. If no reference table is used for the field or the data source does not support the notion of an owner, an empty string is displayed. |
Key | Name of key field of the reference table set for a field. If no reference table is used for the field, an empty string is displayed. |
Value | Name of value field of the reference table set for a field. If no reference table is used for the field, an empty string is displayed. |
Width | Width of displaying a field in centimeters. |
Primary | Name of primary field – field of query on the basis of which the present calculated field is obtained. If the field is not a calculated one, an empty string is displayed. |
Hidden | Indication of invisibility of the field when browsing query records. |
Grouped | Indication that the field makes part of the calculation group. The field is a part of the calculation group if it is neither a calculated field, nor a hidden one (the indication of invisibility of field is not set). |
Calculated | Indication of calculated field. |
Operation | The operation using which the present calculated field is obtained. If the field is not a calculated one, an empty string is displayed. |
Table 42-2. General properties of field of EDB query
The page “Settings” of the property sheet shown at figure 42-11 has much in common with the page of properties of field of internal GDB query with the same name (see chapter 30 “Queries”, figure 30-2).
Figure 42-11. Property sheet “Properties of field” for EDB query, page “Settings”
On this page the indication of a hidden field, width of field display and also the data on setting a reference table for a field are displayed and can be changed. Unlike a field of internal query, there is no checkbox which controls editability of field. The possibility to edit fields of EDB query is determined by user permissions to the corresponding components of the data source and also by other factors described in chapter 38 “Basic notions of external databases”, subsection “EDB queries”.
On page “Special” of the property sheet shown at figure 42-12 the properties supported only by some data sources are presented. The structure and meaning of properties on this page corresponds to the properties of field of EDB table displayed in the pane “Special properties” of the page “General” (see figure 42-4).
Figure 42-12. Property sheet “Properties of field” for EDB query, page “Special”
On page “Permissions” three checkboxes are located. They indicate whether the present user has permission to perform three basic actions with values of the present query field: to update (that is, change field values), insert (that is, set field values when adding records), select (that is, get field value when sending a request to external data source). This page does not differ from the corresponding page of the property sheet of EDB table field shown at figure 42-5.
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