Hi guys,
I know PRIMARY key is to have unique value, what about INDEX? What is the function of a table column with INDEX?
+5
A:
INDEX columns are exactly that. They're indexed to make it faster to look up information using that column. MySQL typically stores Indexes in B-Trees or R-Trees. An appropriate case for the use of an index would be if you're using a where clause on a particular column (or group of columns) regularly.
Indexes are a topic worthy of whole chapters in database books, a good place to start looking for more information might be the mysql reference manual.
Vertis
2009-02-16 03:46:57
It might be appropriate to point out that "faster" in this context can mean "a hell of a lot faster."
Ori Pessach
2009-02-16 03:49:18
And by 'a hell of a lot faster' can often mean a hundred or a thousand or even a million times faster. Seriously!
staticsan
2009-02-16 04:23:52
If my data is not very huge, should I still use index??
roa3
2009-02-16 08:58:13
Yes, with indexes selects will be a lot faster. In order to find an item using index database will not read all data. It'll just look in index and read the item you need.
zihotki
2009-02-18 05:12:14
+1
A:
An INDEX in MySQL, performs the same kind of function an INDEX does at the end of a book. It enables faster lookup for your information when you do a query like:
SELECT * FROM MY-DB-WITH-INDEXES> WHERE <INDEX_FIELD=foo_bar>
Good choice of the columns used to form an index always makes a good database design.
Amit
2009-02-16 03:50:55