Syntax KEY string SELECT ... END
User can define his own KEY(s) that can be later used in SELECT statements. The KEY name can be up to 10 characters long string. When a key and a MAIN tag have the same name, then the KEY value will prevail. In a SELECT sentence the signs like % and * can be used in order to access more than one KEY at a time.
Keys can be DROPPED of INITIALIZED. By DROPPING only the particular KEY is deleted, while by INITIALIZE all defined KEYS are gone. Also by INITIALIZING a string, as a dummy key, must be typed in.
Use SHOW KEY or SHOW SELECTIONS to see the list of defined KEY(s) and number of SELECTED atoms in each one.
When no atom is SELECTED in the specified KEY, a warning message appears.