You should probably create two separate indexes, one on source_url and one on create_date. Unless you are frequently searching on
both source_url and create_date.
Remember that an index is really just sorted data that can be searched quickly.Since create_date will have pretty unique values, it
would be useless to sort on create_date then source_url since almost not source_url would have the same create_date.
But if you first sort on source_url, then create_date (create_date last field in the index), that would be usefull if that's one of
your search patterns.
I usually create two fields, create_date and create_time. Then I can use just the create_date as part of a compound index, which
wouldn't be unique.
----- Original Message -----
From: "wangxu" <[EMAIL PROTECTED]>
To: "Brent Baisley" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Thursday, April 12, 2007 10:13 AM
Subject: Re: Can I create a index on a column of Type datetime?
Thank you,
what 's the meaning of "using a datetime field unless it's the last
field in the index."?
the below is the desc result;Should I create an index on
(source_url,create_date)?
for these two fields are to be often queried by.
+---------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+--------------+------+-----+---------+----------------+
| id | bigint(20) | NO | PRI | NULL | auto_increment |
| create_date | datetime | NO | | | |
| brand | varchar(255) | YES | | NULL | |
| category | varchar(255) | YES | | NULL | |
| description | text | YES | | NULL | |
| detailed_desc | text | YES | | NULL | |
| imageUrl | varchar(255) | YES | | NULL | |
| name | varchar(255) | YES | | NULL | |
| price | varchar(255) | YES | | NULL | |
| properties | text | YES | | NULL | |
| sku | varchar(255) | YES | | NULL | |
| source_url | varchar(255) | YES | | NULL | |
| link_path | varchar(255) | YES | | NULL | |
| site_name | varchar(255) | YES | MUL | NULL | |
| page_score | float | YES | | NULL | |
| tag | varchar(255) | YES | | NULL | |
| dumped | bit(1) | YES | | NULL | |
+---------------+--------------+------+-----+---------+----------------+
Brent Baisley wrote:
You can create an index on just about any field. Just remember that
the data in a datetime field is fairly unique, so it would do much
good to create a compound index (2 or more fields) using a datetime
field unless it's the last field in the index.
----- Original Message ----- From: "wangxu" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, April 11, 2007 8:08 PM
Subject: Can I create a index on a column of Type datetime?
I will very often do query like this:
select * from mytable where create_date >='...' and create_date <='....'
can I create a index on the column create_date?
what is the best practise?
Thanks,
shell.
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