erSQL - the Language
The erSQL language provides a user friendly access to the database. The query language borrowed a few syntactical constructs from (relational) SQL, but is completely different in structure:
- SQL refers to the (logical / physical) data model and is primarily used by specialists
- erSQL refers to the conceptual data model and is designed for users and specialists
The creationg of queries is supported by an interactive graphical query-builder. It uses point and click on the graphical conceptual model to construct the query text and to document the query graphically. The query-builder is integrated in metaEditor and in the Birt-Interface. ...more
The query processor translates the query-text, accesses the database to retrieve the data and returns the results to the invoking system.
- metaEditor: Contains the query-builder as selectable view to crate a query. This query can be executed to display the results in a table as defined by the query builder. metaEditor handles deferred parameters and prompts them to enter the current value.
- Birt-Interface: The query-builder is integrated in the Birt-Designer to create a query and to produce a preliminary report similiar to metaEditor. An erSQL query can be stored and executed directly by the Birt-Processor via the Metasafe ADO-Driver.
- API in a java program: The query text can be embedded in a java program to launch the query processor. The query processor returns a resultset in form of a table of typed attributes.
The "virtual reader" is an alternative to the creation of the entire resultset. A method returns each individual result - i.e. a single line - with all the metadata.