What does the WHERE EXISTS clause do in a load statement?

The WHERE EXISTS clause in a load statement is designed to filter data based on specified conditions, focusing the data set on only those records that meet certain criteria. This clause effectively checks for the existence of one or more values from a field in a previously loaded table. If the condition is met, the records are included in the load; if not, they are excluded.

This is particularly useful when dealing with large data sets, as it allows for more efficient data handling and minimizes the load by including only pertinent records. For instance, if you have a list of customer IDs in a previous table and you want to load only those records from a transactions table that match those IDs, the WHERE EXISTS clause will do just that, ensuring only relevant data is processed and loaded into your Qlik data model. This leads to optimized performance and more relevant insights in your applications.