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<div class="nb-cell markdown" name="md1">
# Managing displayed variables (projections)

Often a query contains variables in which value you are not interested.  This is notably the case when using the __table results__ option, either in the main window or using the settings button for notebook queries.  In addition one may whish to display the variables in a particular __order__.

One of the options for omitting variables from being displayed is to use the _anonymous_ variable `_` or the _named singleton_ notation `_Name`, i.e., a variable whose name _starts_ with an underscore followed by a capital letter.  Such variables are not included in the output.  For example, consider the query below which displays `Y`, but hides `_X`, while this variable is still used to carry information between the two goals.

Note that this way of hiding variables is also used by the normal SWI-Prolog toplevel.
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<div class="nb-cell query" name="q1">
_X = 1+1,
Y is _X**4.
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In SWISH, the above can also be achieved using projection(ListOfVars), as a __first subgoal__ in a query, where `ListOfVars` also dictates the order in which the variables are displayed.  Consider the two queries below.  

A default projection can be added using the __Prejection__ menu option in the hamurger menu (notebooks) or the _Solutions_ menu (main query window).
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<div class="nb-cell query" data-chunk="10" data-tabled="true" name="q2">
Table = 7,
between(1, 10, F),
Value is Table*F,
Expr = (F*Table).
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<div class="nb-cell query" data-chunk="10" data-tabled="true" name="q3">
projection([Expr,Value]),
Table = 7,
between(1, 10, F),
Value is Table*F,
Expr = (F*Table).
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