See what WITH CONNECTION can do for you when working with REST data sources
I was approached by a colleague with a simple but recurrent question, how can I use for…while loops in conjunction with the REST connector, and how can we make it work with the connection library that comes with Qlik Sense.
A few months ago I shared a “hack” so we can do loops in our scripts as we do with QlikView, activating Legacy Mode will make connection library optional, please remember that there are a bunch of good reasons for not do that. “With connection” is a great solution for those of you who don’t want or just can’t activate Qlik Sense Desktop to work in Legacy Mode but still need to loop through several URLs to get complete data.
Let’s do a quick example.
We need to load data from an online data source, we have a URL to connect to the data that contains the ID of each one of the elements that we would like to load into our app.
We have a list of 100 alphanumeric elementIDs and we need to make sure we load them all. Using our REST connector, we could easily connect to the online data source and extract the data, but we faced the issue of how to make to connection loop trough a series of items.
In our example we have an inline table that contains each one of the ID numbers of the elements we want to read in the REST connector, and we need to pass that parameter to the connection URL below.
LIB CONNECT TO 'REST';
ElementsToLoad:
Load * inline [
ElementID
12fa91
1sy293
h13d13
…
];
Let j=0;
for j = 0 to 99
Let vElementID = peek('ElementID', $(j), 'Teams');
RestConnectorMasterTable:
SQL SELECT
fields
FROM "datad")
FROM JSON (wrap on) "root" PK "__KEY_root"
WITH CONNECTION(Url "https://www.domain.com/element?key=$(vElementID)/more_stuff/");
NEXT j;
DROP TABLE RestConnectorMasterTable;
exit Script;
After the inline statement, we loop over the REST connection 100 times, one time for each row of the inline table, I know we have 100 rows so I'm hard coding that number but if you don't know how long your table is you should check that before and store it in a variable.
Lately, using "With Connection" we have access to the data source URL so we can expand my variable "vElementID" containing the necessary ID for the connection to work.
Alright, I looked at your code sample once again, and here's another idea. In each cycle, you need to drop RestConnectorMasterTable to ensure you are populating it with the new data on the next pass. What I do is dumping the current data from RestConnectorMasterTable into another permanent table so I can safely drop it after that.
So create an empty table prior to entering the loop and then add consolidate RestConnectorMasterTable data into it using concatenate.
@Ken_T - Good question! I don't think WHERE is supported in selecting data from a REST connection. See "SELECT statement syntax" section on the page below.
That said, you can try to add additional filters to your URL used in WITH CONNECTION. The same page provides some examples on using URL parameters for pagination.
@ArturoMuñoz Hey Arturo, could you please help with the script?
I am trying to use your script. Data load happens without any error, but it doesn't load any values (loads 0 values). I am attaching a screenshot. Currently there are only two values in [id], but I intend to use a lot more.
