Oracle indexing technology-Daily notes (2)

Oracle indexing technology-Daily notes (2) function indexing SELECT * from demot where F7 = 'F'; SELECT * from demot where lower (F7) = 'F '; there was a bitmap index on F7, but after using the LOWER function, the whole table was scanned. Next we will CREATE the function index lower create index FUN_INDEX on demot (LOWER (F7) ON the F7 column. 5 seconds then looks at the execution plan, and the INDEX scan is used. The aggregate function itself creates an index in oracle. Composite Index/composite index: How do I arrange the column order when creating an index? We recommend that you place the most frequently accessed columns at the top of the index. Avoid using a low base sequence as the index-compliant leading column. The index is created only when different keys in the WHERE clause of the application frequently appear together and are currently using the "and" operation to combine these columns. Create index REV_INDEX on demot (F2) REVERSE; 7 when you CREATE an INDEX in seconds, the value of the INDEX column is reversed before the INDEX is inserted, in this way, the inserted sequence key value will not cause contention for the rightmost index block, and the database will not store the new value to the same "hot" index block, instead, they are stored in new entries that span a large number of blocks to reduce contention for busy blocks. The actual values of the primary key are arranged consecutively, but the index values are not arranged consecutively.