Database Filters

Filters are applied to every record in a database, and only those meeting the criteria will be displayed or used for computations.  This provides a rapid and powerful way to control and subset the data.

Filters must be single conditions, combined with AND or OR.  You cannot say "2<X<6", but must say "(X>2) AND (X<6)".

It never hurts to add extra parentheses to make the intent clear.

Filters can use a wild card.  For instance, volcano types might be coded as "Shield", "Shields", or "Shield (?)" in a database.  To avoid an OR, you could filter for "TYPE='Shield*'" which would cover all three.  You must be sure that there are not other similar variants that you do not want, and know what the wild card symbol is for the data base.  While "*" is common, other databases might use something else like "%".

After you filter a database, any operations like plotting on the map or computing will only use the records which match the filter.

Last revision 9/19/2017