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Using dataset operators in a mapping

    Using a stage is a nice way to manipulate source sets with operatos like UNION, MINUS, INTERSECT, etc.

    • Step 1 : add the desired source table to the mapping
    • Step 2 : add a stage
    • Step 3 : on the stage, add Sets and map source columns to each set
    • Step 4 : in the expression editor of the stage, specify the desired expression, for example: [A] union ( [B] minus [C] )

     

     

    How to Pivot or Unpivot a table

      Using Query

      If you are working on a database that is capable of pivoting or unpivoting tables, you can simply write a query that makes the transformation and reverse it in Stambia.

      Here is an example of how to do it using MSSQL Pivot operator.

      Write a query that gives you the desired transformed table in MS SQL:

       MS SQL Query

      In the MS SQL metadata create a new query folder and a new query. Give it a name and paste the query:

       Query in metadata

      Save the metadata and the right click on query and choose Reverse from Actions:

       Reverse query

      Save the metadata again and now you can use the result of the query as a source in your mappings:

      Reversed query in a mapping

      Using Stages

      In all other cases it is possible to make this kind of transformation in Stambia using stages.

      Note if you do not have a database that you can use to create a stage you can use the internal H2 database included in the runtime (How to use internal H2 database?)

      Example of pivot:

      In this example we have a source table with a single line per quarter and we want to transform that to have a single line with 4 columns containing values per quarter.

       Source unpivoted table

      To do that we will need to add to our mapping four stages. Each Stage will be alimented with values from one quarter only (you need to add appropriate filter on each:

       Pivot mapping

      The stages should be then joined so they can be used to feed the columns of the target table:

       Pivoted target table

      Example of unpivot:


      We can also imagine a situation where in the source of our mapping we have a table with quarterly values in columns and we want to feed a target table where each quarterly value will be represented in one line.

      In this case we will need one stage with four sets:

       Unpivot mapping

      Each set represents a quarter with QNO value hardcoded and corresponding value mapped from source table. All sets are combined with UNION operator and can be used to feed the target “unpivoted” table.

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