Dropping tables and fields in Qlik

Every Friday at Bitmetric we’re posting a new Qlik certification practice question to our LinkedIn company page. Last Friday we asked the following Qlik Data Architect certification practice question about dropping fields and tables in Qlik Sense and QlikView:

The correct answer is D: DROP FIELD [Fieldname] FROM [Tablename];

The correct way to drop a field after it is no longer needed in Qlik is to use the drop statement. Since the drop statement is also used to drop tables, it is needed to specify what you are going to drop. In this case there are some possibilities. To specify the field or the fields you want to drop. And optionally if you want to drop them from a specific table. The options are demonstrated in the figure below:

So starting with the drop statement we can choose to drop all fields using the following syntax:

DROP FIELD a;

However, be aware that this is only applicable to the tables loaded until that line. All tables loaded after that drop statement containing field a, will still load field a. In best practice if you want to remove those fields, use this in a clean up section at the end of the whole load script.

When using a clean up script, it might very well be possible, that some of those fields need to be dropped, while others need to be kept. For example in case when link tables are created. It is then possible to specify from which table to drop the field with the following syntax:

DROP FIELD a FROM x;

Here field a is only dropped from table x, leaving all other instances of field a in their respective tables.

Dropping multiple Qlik fields and tables at once

If we would like to drop multiple fields or tables, it is simply done by using the plural and adding the field or table names separated by a comma:

DROP TABLES x, y;

In this case the tables x and y are dropped from the data model. Needless to say is that there is no option to choose to drop the tables from any other table ;).

That’s it for this week. See you next Friday?

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