SET AND gives the connecting operator AND precedence over OR in WHERE, IF, and WHILE conditions. When on, R:BASE processes conditions in the following order:
AND NOT
AND
OR
SET AND OFF directs R:BASE to process conditions from left to right. The WHERE clause A AND B OR C AND D is evaluated as (((A AND B) OR C) AND D). SET AND ON directs R:BASE to give the operator AND precedence over OR. The WHERE clause A AND B OR C AND D is evaluated as ((A AND B) OR (C AND D)), which is a different result set.