% @(#)createvirt.hlq	19.1 (ESO-IPG) 02/25/03 14:03:12
% @(#)createtabl.hlq	7.1 (ESO-IPG) 2/24/94 18:30:51 
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      createvirt.hlq
%.AUTHOR     MP, IPG/ESO
%.KEYWORDS   MIDAS, help files, CREATE/VIRT
%.PURPOSE    On-line help file for the command: CREATE/VIRTUAL
%.VERSION    1.0  1-MAR-1994 : Creation, MP
%----------------------------------------------------------------
\se
SECTION./VIRT
\es\co
CREATE/VIRTUAL						1-MAR-1994   MP
\oc\su
CREATE/VIRTUAL  virtual table
	create a virtual table from a physical table
\us\pu
Purpose:      
             Create a virtual table from a physical table. 
             A virtual table doesn't contain any real data except
             for a selection column. Its other columns are assembled at
             run-time from the columns of the physical table.
\up\sy
Syntax:       
             CREATE/VIRTUAL  virtual table
\ys\pa
             virtual    = name of the output virtual table 
\ap\pa
             table      = name of the physical table  
\ap\no
Note:        
             No operation modifying the contents of a table is allowed on 
             a virtual table except for the SELECT/TABLE operation. 
             A virtual table may be projected or copied into a physical 
             table. 
             Virtual tables may be used, for instance  to access and manipulate
             local databases, i.e read-only tables without copying these tables
             into a private directory:

             CREATE/VIRTUAL esolv_virtual /midas/calib/data/esolv
               creates a virtual table esolv_virtual from the physical table 
               /midas/calib/data/esolv
             SELECT/TABLE esolv_virtual seq.le.1000
               selects the first 1000 entries of the virtual table esolv_virtual
             COPY/TABLE esolv_virtual myesolv
               copies the selected entries of esolv_virtual into a physical table
               myesolv

             The name of the physical table from which the virtual table is created is
             stored into the descriptor TVIEWTBL of the virtual table.

\on\see
See also:
             CREATE/TABLE
\ees\exs
Examples:
\ex
             CREATE/VIRTUAL esolv_virtual esolv 
             creates the virtual table esolv_virtual.tbl from the table esolv.tbl
\xe\sxe
