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09.2. How to add a column to the results table
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**RSP Aspect:** Portal

**Contact authors:** Greg Madejski and Melissa Graham

**Last verified to run:** 2025-02-04

**Targeted learning level:** beginner 

**Introduction:**
This tutorial demonstrates how to derived new columns from retrieved columns in the Portal results tab.

**1. Execute a query.**
Go to the Portal's DP0.2 Catalogs tab, switch to the ADQL interface, and execute the query below.
This query will retrieve a small sample of point-like objects (stars) brighter than 25th magnitude (as in preceding tutorials).

.. code-block:: SQL

  SELECT coord_dec, coord_ra, detect_isPrimary, refExtendedness, 
         u_cModelFlux, g_cModelFlux, r_cModelFlux, 
         i_cModelFlux, z_cModelFlux, y_cModelFlux 
  FROM dp02_dc2_catalogs.Object 
  WHERE CONTAINS(POINT('ICRS', coord_ra, coord_dec), 
        CIRCLE('ICRS', 62, -37, 0.167)) =1 
        AND (detect_isPrimary =1 AND refExtendedness =1 
             AND u_cModelFlux >360 AND g_cModelFlux >360 
             AND r_cModelFlux >360 AND i_cModelFlux >360 
             AND z_cModelFlux >360 AND y_cModelFlux >360)


**2. View the default table** (Figure 1).
Only one query has been executed, so there is only one tab in the table panel (A in Figure 1).

.. figure:: /_static/portal-howto-table-1.png
    :name: portal-howto-table-1
    :alt: The default view of the table panel.

    Figure 1: The table panel that results from the query in step 1. The third row has been clicked on and is highlighted orange.


**3. Open the "Add a column" window.**
Click on the "add column" icon (H in Figure 1) to open the pop-up window in Figure 2.

.. figure:: /_static/portal-howto-table-5.png
    :name: portal-howto-table-5
    :alt: The pop-up window to add a new column, with entry field boxes to define the derived column.

    Figure 2: The pop-up window to add a new column, with entry field boxes set to define a new derived column of g-band AB magnitudes.


**4. Define the new column.**
New columns can only be derived from pre-existing columns using an expression.
In the pop-up window, name the new column ``g_cModelMag``.
Use the following expression, which converts fluxes (in units of nJy) into AB magnitudes: ``-2.5 * LOG10(g_cModelFlux) + 31.4``.
Provide the units of the new column as ``mag``, and add a description.
Click "Add Column", and it will appear in the table.

**5. Option to save the table.**
Click on the save icon (G in Figure 1), choose a file format of comma-separated values (CSV) and name the file as "my_table.csv".
Leave the default selection of "Save table as displayed" in order to include the new derived column of g-band magnitudes, and click "Save" to download the file.


.. figure:: /_static/portal-howto-table-6.png
    :name: portal-howto-table-6
    :alt: The pop-up window to save a table.

    Figure 3: The pop-up window to save a table, with the selections as described in step 5.


Return to the list of DP0.2 :ref:`DP0-2-Tutorials-Portal`.