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Input/Output tables

If a SELECT command finds observations in the input table which satify the search specification, a new output table is created, which becomes the default input table for the next command. Thus, if the three commands shown above were to be given sequentially, the SEL INI command creates table 1 (table 0 being the catalogue), the SEL DET command then uses table 1 as input and creates table 2, and finally the SEL OBJECT command creates table 3.

If you would like to do a search again of the catalogue, you can specify the input table explicitly in the select command:

SEL/INP=0 INI=BMW : get data taken by BMW from the catalogue

Or, the table counter could be reset beforehand with:

DEFAULT INPUT_TABLE=0

before doing the SELect. Note that tables 1, 2 etc. can now, in principle, be overwritten with subsequent SELections. However, before an existing table is actually overwritten, the user will have to confirm it, or to define a new output table. In any case, care should be taken if one of those tables contains (part of) the final selection for a request!

The output table can also be specified at will in the select command, e.g. :

SEL/INP=3/OUT=2 OBJECT=NGC4151*

which overwrites the existing table 2. If no output table is specified, the input table name, either explicitly specified or the default, is used to define the default output table.

The table qualifiers can, for instance, be used to limit the number of scratch tables, which otherwise could easily fill up the work space of the captive account. Tables can also be DELeted; several tables can be combined in one output table with Union, DIfference, or Intersection (section ). Thus, by intelligently using the select and table-handling functions, a user can compose a final table with observations of interest, and submit a request to de-archive those observations.