![]() When configuring a column reference, the fields Table and Column are used to select the column(s) to be used in the reference. The next field Used in is where the reference is placed in the view's definition, we will talk in details about this field soon. type to configure a reference from a table, column or expression. Let's detail this situation based upon the image below. In pgModeler these elements are the view references and they behave differently depending on the portion of the SQL definition they are placed. Looking carefully to the complete command above we can notice that there are elements between keywords SELECT and FROM, FROM and WHERE, and after the WHERE. Finally, boolean_expr is a filtering clause being a SQL expression that returns a boolean result. The elements ca, cb, expr, ta and tb are the aliases assigned to their respective identifiers. The next elements, tableA and tableB are the table identifiers. The elements col1, col2 are column identifiers and now() + interval '1 hour' is a simple SQL expression. Generally, a view's definition is a simple select command as follow: The main advantage to use these references is that user don't need to write the complete command to generate the view, also any reference to columns and tables are automatically updated when the referenced objects have their names changed. These objects are responsible to generate portions of the DDL that, in the end, will form the whole view's definition. In order to keep track of column's and table's names pgModeler constructs views in the database model using objects called references. This tab provides a preview of SQL code which produces the view as the user configures the attributes on the form. These queries are commonly known as Common Table Expression as stated by the PostgreSQL docs. This tab is used to configure auxiliary queries to be executed together with the view's SQL definition. This tab is used to configure indexes to be assigned to the view. This tab is used to configure rules to be assigned to the view. This tab is used to configure triggers to be assigned to the view. More details about references can be seen on the next subsection. These references are used to construct the view's SQL definition. This tab is used to create view references. Indicates that the materialized view should not be populated at creation time. Materialized indicates that a materialized view must be created, which means that the view is populated once and need to be refreshed using REFRESH MATERIALIZED VIEWcommand. Ordinary means that the view is a common one (refreshed everytime it is referenced). Tags are used to graphically separate tables and views even if they are owned by the same schema. This attribute is used to configure the tag object associated to the view. Currently, the implementation of views in pgModeler can't infer precisely the column names of a view which means that it's not possible to make references between views, only between a view and other tables. In that dialog its possible to create a view or a materialized view just by checking the respective option and setting the needed attributes to correctly create both kinds. For the materialized view its definition query is executed and used to populate it at the time the command is issued being possible to refresh its data later by running the special instruction REFRESH MATERIALIZED VIEW.ĭespite the way PostgreSQL treat both views and materialized views, in pgModeler they are treated as a single object handled by the same dialog. The ordinary view is not physically materialized, instead, the query is run every time the view is referenced in a query. In PostgreSQL there're two kinds of views: the ordinary ones and the materialized ones. Once created a view it'll work like a table in the way data is stored and retrieved. Views are objects generated from queries which reference one or more tables or even use ordinary SQL expressions to compose their data.
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