Seclude records in a table that do not satisfy a certain condition
SET FILTER TO [<condition>]
SET FILTER ON | OFF | (<expL>)
If SET FILTER TO <condition> is specified, records that do not satisfy the specified <condition> are automatically secluded. If SET FILTER TO is specified, without a <condition>, the current filter is removed allowing all records to be accessed. The filter <condition> is specific to each workarea, and is removed when a table is closed, or the workarea is re-used. However, the FILTER condition can contain references to fields in related tables. The FILTER() function can be used to save the current filter <condition>. The SET FILTER command enables or disables the filtering process. By default, FILTER is ON.
use patrons set filter to event = "BALLET" and date < date() browse
Recital Server, Recital