On May 21, 2008, at 8:46 AM, Paul McCullagh wrote:
On May 21, 2008, at 8:09 AM, Moon's Father wrote:
Now I want to know which way you use to create index of a table.
1、ix_u (item_id,item_count)
ix_item_count (item_count)
This makes sense if you have queries which search "item_id AND
item_count", and queries which just search the column 'item_count'.
On second thoughts, this answer is not complete.
If this is case then the index ix_u (item_count, item_id) would be the
best choice.
These indices:
ix_u (item_id,item_count)
ix_item_count (item_count)
are best when you have the following types of queries:
WHERE item_id AND item_count ----> the server uses ix_u
(item_id,item_count)
WHERE item_id ----> the server uses ix_u
(item_id,item_count)
WHERE item_count ----> the server uses x_item_count
(item_count)
2、ix_u (item_id,item_count)
ix_item_id (item_id)
This is duplication of the indexing of the column 'item_id'. The
server is able to use the index ix_u (item_id,item_count) to search
on the column 'item_id'.
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