This example also uses table t1 as defined in Example: Creating a Join Index With a Period Column in its Select List to create a join index with a BEGIN bound function in its select list.
CREATE JOIN INDEX ji_begin AS SELECT b1, c1, BEGIN(d1) AS b FROM t1;
If you then submit a HELP JOIN INDEX request on ji_begin , the system returns a report like the following.
HELP JOIN INDEX ji_begin; Column Name Type Comment -------------------------- --------- --------------------- b1 I ? c1 I ? b DA ?
Column b in ji_begin can be used to map an identical query expression such as BEGIN(d1).
For example, the Optimizer can take the following request:
SELECT b1, c1, BEGIN(d1) FROM t1;
and map it to this request that uses the join index:
SELECT b1, c1, b FROM ji_begin;
Or it can take the following request:
SELECT b1,c1 FROM t1 WHERE BEGIN(d1) < '2008-05-01';
and map it to this request that uses the join index:
SELECT b1,c1 FROM ji_begin WHERE b < '2008-05-01';