Qlikview Data Model and best practices
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Qlikview Data Model,Exporting Images & Structures and best practices:
QlikView Data Model best practices dictate that, a star schema is desirable whenever possible. If not a star schema, the smallest possible snowflake schema is fine, especially in limiting the fact tables to one. A scenario may exist, however, where there is only one large fact table containing many dimensions.
Similarly, if you have a data model with a snowflake schema, working to consolidate the data and build a star schema is usually not going to cause increased performance/ decreased time of query in most cases. This does change with very large data sets, and in those cases, it is worthwhile to spend the time to consolidate and collapse as much as you can, to confirm the star schema.
One of the key considerations is limiting the number of connections required for QlikView to access data, so when working with large data sets, consolidate your data and limit the number of dimension tables, as well as consolidate/concatenate multiple fact tables.
Exporting Images and Structures:
The Table Viewer can export images or structures of the existing data model in a QlikView document. These images or structures can be useful in documentation and analysis of a QlikView application. The Table Viewer menu bar, as shown in the following screenshot, can be used for any of the exporting or print commands.
The data model viewer provides you with an overview of the data structure of the app. You can preview the data in the tables and fields in the data model viewer. You can also create dimensions and measures on-the-fly. In the data model viewer, each data table is represented by a box, with the table name as the title and with all fields in the table listed. Table associations are shown with lines, with a dotted line indicating a circular reference. When you select a table or a field, the highlighting of associations instantly gives you a picture of how fields and tables are related.
Table Viewer menu commands help you with the exporting, copying, or printing of data model images and structures, as described in the following lists. Note that the Internal Table View and Source Table View drop-down list options are discussed in the next section, named ‘Viewing internal and source tables’.
Internal Table View is the default option and shows how the data is stored in QlikView. It also shows synthetic keys if they are created.
Source Table View shows how QlikView reads the data and if synthetic keys are present it does not show them.
- Export Image: This menu command allows you to export the image to either a .png or .bmp file. The default file type is .png, and the default location is the current QlikView document directory.
- Export Structure: This menu command allows you to export the current data model to three text files (one each for tables, fields, and mappings). These tables can be imported back into QlikView for the analysis on relationships and statistics.
- Print: This menu command allows you to print a graphical representation of the current QlikView data model, as currently depicted in Table Viewer.
- Copy Image: This menu command allows you to copy the current data model as shown in Table Viewer to the clipboard. This allows pasting the copied data model into a document, email, or graphic editing software.
- Auto-Layout: This menu command allows you to automatically arrange the tables and connections in the data model. This can be a useful starting place for you to then manually clean up the data model and continue moving tables. Note that tables should be arranged prior to exporting, printing, or copying the data model image.
- Zoom: This menu command allows you to zoom in or out of the data model image in Table Viewer.
The layout of tables in the Table Viewer generally persists even when the document is closed and re-opened. However, changing the data models slightly can make the tables in the Table Viewer appear in different locations than the ones previously defined.
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