All components of external data source included into the structure of EDB are considered to be EDB tables which are in many aspects similar to internal tables of ObjectLand but which do not support all the operations applicable to internal tables. EDB queries are created on the basis of one or several tables. To get query records ObjectLand sends a request to the data source which contains SQL statement SELECT. This statement is formed either automatically on the basis of user actions by constructive forming of the query in the course of browsing EDB table or it is written by the user in SQL language directly. EDB layers are special type of components designed for storing spatial data.
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