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### 5.1 Concatenating Tables

Two tables can be concatenated using the Concatenation Window, which just requires you to specify the two tables to be joined, and for each column in the first ("Base") table, which column in the second ("Appended") table (if any) corresponds to it. The Apparent Table is used in each case. The resulting table, which is added to the list of known tables in the Control Window, has the same columns as the Base table, and a number of rows equal to the sum of the number of rows in the Base and Appended tables.

As a very simple example, concatenating these two tables:

       Messier   RA       Dec      Name
       -------   --       ---      ----
       97        168.63   55.03    Owl Nebula
       101       210.75   54.375   Pinwheel Galaxy
       64        194.13   21.700   Black Eye Galaxy

and

       RA2000    DEC2000   ID
       ------    -------   --
       185.6     58.08     M40
       186.3     18.20     M85

with the assignments RA->RA2000, Dec->DEC2000 and Messier->ID would give:

       Messier   RA       Dec      Name
       -------   --       ---      ----
       97        168.63   55.03    Owl Nebula
       101       210.75   54.375   Pinwheel Galaxy
       64        194.13   21.700   Black Eye Galaxy
       M40       185.6    58.08
       M85       183.6    18.20

Of course it is the user's responsibility to ensure that the correspondance of columns is sensible (that the two corresponding columns mean the same thing).

You can perform a concatenation using the Concatenation Window; obtain this using the Concatenate Tables () button in the Control Window.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk