QlikView Design Blog : Preceding Load

green_loaderQlikview blog has posted a great tutorial on Preceding Loads in Qlikview. What is preceding load?

It is a way for you to define successive transformations and filters so that you can load a table in one pass but still have several transformation steps. Basically it is a Load statement that loads from the Load/SELECT statement below.

Example: you have a database where your dates are stored as strings and you want to use the QlikView date functions to interpret the strings. But the QlikView date functions are not available in the SELECT statement. The solution is to put a Load statement in front of the SELECT statement: (Note the absence of “From” or “Resident”.)

Load Date#(OrderDate,’YYYYMMDD’) as OrderDate;
SQL SELECT OrderDate FROM … ;

What happens then is that the SELECT statement is evaluated first, and the result is piped into the Load statement that does the date interpretation. The fact that the SELECT statement is evaluated before the Load, is at first glance confusing, but it is not so strange. If you read a Preceding Load as

Load From ( Select From ( DB_TABLE ) )

then it becomes clearer.

I am reminded from from instance in an application that you can have multiple load statements stacked up before the select statement.
See on community.qlikview.com

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