6 Replies Latest reply: Oct 27, 2014 12:03 AM by jagan mohan rao appala RSS

    Exists?

      what is the Exists how do they works?

        • Re: Exists?

          Can you plz explain about Exists in Detail.

            • Re: Exists?
              Ashfaq Mohammed

              Check the below link

              http://community.qlik.com/message/583198#583198

               

              Regards

              ASHFAQ

              • Re: Exists?
                Anand Chouhan

                Hi,

                 

                From the QV help for explaining the Exists

                 

                These functions are used when a value from previously loaded records of data is needed for the evaluation of the current record.

                exists(field [ , expression ] )

                Determines whether a specific field value exists in a specified field of the data loaded so far. Field is a name or a string expression evaluating to a field name. The field must exist in the data loaded so far by the script. Expr is an expression evaluating to the field value to look for in the specified field. If omitted, the current record’s value in the specified field will be assumed.

                Examples:

                exists(Month, 'Jan') returns -1 (true) if the field value 'Jan' is found in the current content of the field Month.

                exists(IDnr, IDnr) returns -1 (true) if the value of the field IDnr in the current record already exists in any previously read record containing that field.

                exists (IDnr) is identical to the previous example.

                Load Employee, ID, Salary from Employees.csv;
                Load FirstName& ' ' &LastName as Employee, Comment from Citizens.csv where exists (Employee, FirstName& ' ' &LastName);
                Only comments regarding those citizens who are employees are read.

                Load A, B, C, from Employees.csv where not exists (A);
                This is equivalent to performing a distinct load on field A.

                 

                Regards,

                Anand

              • Re: Exists?
                jagan mohan rao appala

                Hi Sampath,

                 

                Check this example:

                 

                Course_id, Student_id

                1,1

                1, 2

                2,3

                2,4

                 

                Course_id, Name

                1, C

                2, C++

                3, Java

                4, Hibernate

                 

                Suppose if you want to load only the courses which has student ID, then Exists comes handy, check below

                 

                StudentCourse:

                LOAD

                *

                FROM StudentCourse;

                 

                Course:

                LOAD

                *

                FROM Course

                WHERE Exists(Course_id);

                 

                Now Course table has only 1 and 2, because 3 and 4 do not have any student_ids assigned.

                 

                Refer Qlikview help file (F1) for more detailed help, it has lot of examples.

                 

                Hope this helps you.

                 

                Regards,

                Jagan.