Data Modelling QlikView
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The document provides tips for improving the performance of data loads in Qlik Sense, including loading from compressed QVD files which is 10-100 times faster than other file types, reducing unnecessary joins and associations between tables, and using techniques like partial loads, link tables, and interval matching to optimize the data model. It also discusses separating load scripts into tabs for each table, implementing access controls through hidden scripts, and binary loading of other Qlik scripts.
Data Modelling QlikView
- 1. 1. Load Statement: Load from Files,xls,csv,qvd,SAP,cloud & other. Load from Db using connect ODBC. Load using SQL Query directly. 2. 10-100 times faster to read files from QVDs as these are compressed data files. 3. Association (Relationship between tables) more than 1 associated field synthetic keys are generated.
- 2. 4. During load of multiple tables 2 or more tables get associated based on multiple field names (columns) generating synthetic keys and synthetic tables. They are resource intensive hence must be removed. 5. Loops 3 or more tables making circular reference. Loosely couple tables or aliases remove loops.
- 3. 6.Reduce no. of tables and join in data model. Use mapping tables and ApplyMap(). 7. Inline tables create small ref tables, create inline tables. 8. Joins : left keep like left outer join. 9. Scripts: separate scripts for each tables into tabs 10. Create master calendar when no continuous dates in fact table.
- 4. 11. Concatenated tables: tables with similar field names can be concatenated help resolve synthetic keys. 12. Link Table: link 2 fact tables contain common keys from both eliminate need for multiple key join of synthetic keys. 13. Partial Load: load a subset of tables. ADD will append records and REPLACE drop and create table
- 5. 14. Cross Table: prefix CrossTable to load statement. performing aggregation is difficult. 15. Section access: provide data level security restricting what users can see. Access defined by hidden script. Access control data managed through text files,db and inline tables. 16. Binary load: used to load script part of another qvw file. 17.Interval match start end interval data to single discrete value.Also for slowly changing dimension.