DB_SELECT

COMMAND TYPE : SELECTION

PURPOSE:

This command extracts fields from a catalogue.

DESCRIPTION:

With this command you can extract fields from a catalogue selecting only the records that satisfy the wanted constraints. The constraints can be set on coordinates by a specific input form or on the other fields using the query language statements. When the user sets constraints on coordinates and the original catalogue is sorted with respect to a coordinate this routine uses a very fast dichotomy search strategy.

When no constraints are present this command copies by columns an original catalogue or modify the fields order.

INPUT FIELDS of the command:

From: PDB ?

The user must enter Y when the input catalogue is in Personal Data Base.

Example : Y

Catalogue Name

The name of the input catalogue.

Example : UGC

Select:

User must enter the name of the fields of the input catalogue that will be extracted and written in the output file. The field names must be divided by space or by comma. The following special keywords can be used:

%ALL Returns all the fields of the input cat.

%REC Returns the record number of the input cat.

Example : RA DEC MAG %REC

The CTRL-L key provides more rows to write field names.

Where

The user must insert the constraints on the fields of the input catalogue that will be used for the search. Only the records that comply with this filter will be picked-up in the output file. Refer to Query Language chapter to have explanations about the statements and the available functions. The user can set constraints on all the fields of the input catalogue and on function of it. The next window can be used to set constraints on the coordinates.

Example : MAG < 13 AND (MAG-MAGV) < 1.5

The CTRL-L key provides more rows to write constraints.

Set/Modify constraints on coordinates ?

The user can set constraints on the coordinates answering Y to this question. A new window will be opened on the screen and the user will define the name of the coordinate fields and the limits of the sky region. When coordinate constraints are defined these remain active even if this field is set to N. The only way to remove these constraints is to set to zero all the values of the limits.

Example : Y

INPUT FIELDS of the coordinate window:

1Coordinate

The user must enter here the name of the first coordinate of the sky zone that he needs to select. First coordinates can be Right Ascension, galactic longitude and so on.

Example : RA

>From : To:

The user must enter the limits of the sky zone on the first coordinate. A message on the screen shows the units to be used (hours or degrees). When both these fields are set to 0 0 0 the sky zone has not bound in the first coordinate.

Example : 10 20 35.00 10 45 00.00

2Coordinate

The user must enter here the name of the second coordinate of the sky zone that he needs to select. Second coordinates can be declination, galactic latitude and so on.

Example : DEC

>From : To:

The user must enter the limits on the second coordinate of the sky zone. Units are degrees. The values must be entered from South to North. When both the fields are set to 0 0 0 the sky zone has not limits in the second coordinate.

Example : -30 20 00.00 -27 20 00.00

Output: File Name

The name of the output file that contains the fields selected from the input catalogue.

Example : NEWCAT2.DAT

PDB Catalogue Name

The name of the new catalogue in the Personal Data Base. When this field is filled an entry in the PDB for this new catalogue will be created and the user can continue to work on these new data with DIRA. Otherwise only the output file will be written. Valid catalogue names are strings of 12 or less characters that do not contains special symbols.

Example : NEWCAT2



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