----------  Variables  ----------

The   Empress  Query  Language  maintains  a  list  of   character-string
variables,   much  like  the  UNIX  shell.   Initially,  the list of variables
is  exactly  the  environment  passed  to  Empress ,  i.e.  the  exported
shell   variables .   You  may  print  the  variables,  add  (set)  new  ones,
remove (unset) old ones, and  change  and  use their values.

To use the value of a variable in any query language command, use the  formula
"$VARIABLE".  For example, after entering the command:

        set pers to "from personnel";

typing

        select $pers;

is equivalent to typing

        select from personnel;

Where it is necessary to separate the  formula  "$VARIABLE"  from  surrounding
characters,  the  formula "${VARIABLE}" must be used instead.  For example, if
you have a table called "personnel_file", typing

        select $pers_file;

will result in an error as the variable "pers_file" is not defined.   Instead,
you must type

        select ${pers}_file;

in order to obtain the equivalent:

        select from personnel_file;

The name of a variable is restricted to be a string of alphanumeric characters
of any length.  The variable expansion character (default $) is defined in the
system MSQLVARCHARS.  To prevent this character from causing an attempt to ex-
pand a variable, it must be doubled; ie. "$$p" evaluates to the string "$p".

For further information on how to set, show or unset variables, enter:

                help set;
                help show;
