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Answer Posted / sa123
For good performance Index is required.
Consider the case of a very large table (20,000,000 rows)
to which new records are added daily (usually about 1,000
of them). Every night, you need to report these additions
on an audit trail. Rather than scan the whole table looking
for changes, you will want to use an index over the
TRANSACTION_DATE column. But the index would need to be
huge. This is a case in which your index is over the entire
table, although you are actually interested only in the
1,000 or so records that were added today. The actual index
is physically many times larger than it needs to be, and it
uses many more disk I/Os to traverse the binary tree to the
leaf data.
| Is This Answer Correct ? | 8 Yes | 2 No |
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