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Re: Storing dates [message #186263 is a reply to message #186252]

Sun, 22 June 2014 12:38

Thomas 'PointedEars'
Messages: 701
Registered: October 2010

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Senior Member

[F'up2 comp.databases]

Tim Streater wrote in comp.databases.mysql and comp.lang.php:

> Jerry Stuckle wrote:
>> On 6/21/2014 5:06 PM, Tim Streater wrote:
>>> I have a field which contains values like 3.7, 4.2, etc. But when I
>>> defined the field (in SQLite) I made it a TEXT field, forgetting that I
>>> would need to be able to sort on that field.
>>>
>>> My workaround is to convert the string to floating at the time of the
>>> sort. In SQLite I do:
>>>
>>> ... ORDER BY ROUND(myfield,1);
>>>
>>> which works just fine. Richard should look for something similar in
>>> mysql.
>>
>> Why don't you fix your database?
>>
>> The way you're doing it cannot use an index and will call round() for
>> EVERY row in the sort.
>
> I'd have to ask a number of users to convert their data when they next
> upgrade the software. Trouble is in SQLite you can't just redefine a
> table column to be a different type; ALTER TABLE is somewhat limited.
> I'd have to copy the whole table to another, DROP the first one, RENAME
> the new one, VACUUM the database to get its size down.

True, but see also “Making Other Kinds Of Table Schema Changes” in
<http://www.sqlite.org/lang_altertable.html>.

> OK, it's doable,
> but I'm replying on less-than-technically-savvy users to run a Terminal
> script on their own machine to effect this change.

If this is for an Android app (where SQLite is prevalent), you can use
built-in versioning support to migrate the SQLite database table structure
automagically with the next upgrade or downgrade. BTDT.

<http://developer.android.com/guide/topics/data/data-storage.html#db>
< http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHe lper.html>

Otherwise you can have a table with corresponding version information. If
it is missing or the corresponding record is missing, you can assume the old
format and migrate the data accordingly. Several SQL-based applications do
this.

For example, Magento (which by default is MySQL-InnoDB-based) holds the
version of an extension in the table `core_resource`, and you can write
migration scripts (named e.g. upgrade-$old_ver-$new_ver.php) that are
automatically run if the current version differs but matches $old_ver, and
the new extension version matches $new_ver, after which the version in
`core_resource` is updated automatically to $new_ver.

PointedEars
--
Sometimes, what you learn is wrong. If those wrong ideas are close to the
root of the knowledge tree you build on a particular subject, pruning the
bad branches can sometimes cause the whole tree to collapse.
-- Mike Duffy in cljs, <news:Xns9FB6521286DB8invalidcom(at)94(dot)75(dot)214(dot)39>

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[Message index]

		Putting it all together By: Mr Oldies on Fri, 20 June 2014 14:20
		Re: Putting it all together By: Evan Platt on Fri, 20 June 2014 15:11
		Re: Putting it all together By: Mr Oldies on Fri, 20 June 2014 15:24
		Re: Putting it all together By: Doug Miller on Fri, 20 June 2014 17:15
		Re: Putting it all together By: Evan Platt on Sat, 21 June 2014 03:01
		Re: Putting it all together By: Jrgen Exner on Fri, 20 June 2014 15:21
		Re: Putting it all together By: Norman Peelman on Sat, 21 June 2014 01:06
		Re: Putting it all together By: Denis McMahon on Sat, 21 June 2014 03:02
		Re: Putting it all together By: Denis McMahon on Sat, 21 June 2014 03:09
		Re: Putting it all together By: Jrgen Exner on Sat, 21 June 2014 03:13
		Re: Putting it all together By: Mr Oldies on Sat, 21 June 2014 03:34
		Re: Putting it all together By: Jrgen Exner on Sat, 21 June 2014 03:48
		Re: Putting it all together By: Evan Platt on Sat, 21 June 2014 04:00
		Re: Putting it all together By: Doug Miller on Sat, 21 June 2014 04:22
		Re: Putting it all together By: Jrgen Exner on Sat, 21 June 2014 05:11
		Re: Putting it all together By: Evan Platt on Sat, 21 June 2014 05:39
		Re: Putting it all together By: gordonb.zp2md on Sat, 21 June 2014 09:15
		Storing dates (was: Putting it all together) By: Thomas 'PointedEars' on Sat, 21 June 2014 10:15
		Re: Storing dates By: Mr Oldies on Sat, 21 June 2014 15:10
		Re: Storing dates By: Doug Miller on Sat, 21 June 2014 17:42
		Re: Storing dates By: Mr Oldies on Sat, 21 June 2014 18:28
		Re: Storing dates By: Jrgen Exner on Sat, 21 June 2014 19:04
		Re: Storing dates By: Doug Miller on Sat, 21 June 2014 19:06
		Re: Storing dates By: Tim Streater on Sat, 21 June 2014 21:06
		Re: Storing dates By: Jerry Stuckle on Sat, 21 June 2014 21:09
		Re: Storing dates By: Tim Streater on Sat, 21 June 2014 21:33
		Re: Storing dates By: Jerry Stuckle on Sat, 21 June 2014 21:49
		Re: Storing dates By: Thomas 'PointedEars' on Sun, 22 June 2014 12:38
		Re: Storing dates By: Jrgen Exner on Sat, 21 June 2014 21:31
		Re: Storing dates By: Tim Streater on Sat, 21 June 2014 21:44
		Re: Storing dates By: Thomas 'PointedEars' on Sun, 22 June 2014 12:59
		Re: Storing dates By: Denis McMahon on Sat, 21 June 2014 23:19
		Re: Storing dates By: Arno Welzel on Sun, 22 June 2014 06:53
		Re: Storing dates By: Erick T. Barkhuis on Sun, 22 June 2014 08:03
		Re: Storing dates By: Jerry Stuckle on Sun, 22 June 2014 13:29
		Re: Storing dates By: Erick T. Barkhuis on Sun, 22 June 2014 14:24
		Re: Storing dates By: Jerry Stuckle on Sun, 22 June 2014 14:32
		Re: Storing dates By: Erick T. Barkhuis on Sun, 22 June 2014 14:45
		Re: Storing dates By: Denis McMahon on Sun, 22 June 2014 19:44
		Re: Storing dates By: Jrgen Exner on Sun, 22 June 2014 15:26
		Re: Storing dates By: gordonb.q26od on Sun, 22 June 2014 15:00
		Re: Storing dates By: Arno Welzel on Sun, 22 June 2014 14:47
		Re: Storing dates By: Mr Oldies on Sun, 22 June 2014 17:55
		Re: Storing dates By: Jrgen Exner on Sun, 22 June 2014 19:31
		Re: Storing dates By: Thomas 'PointedEars' on Tue, 24 June 2014 20:27
		Re: Storing dates By: Denis McMahon on Sun, 22 June 2014 19:52
		Re: Storing dates By: Arno Welzel on Sun, 22 June 2014 19:52
		Re: Storing dates By: Mr Oldies on Sun, 22 June 2014 18:05
		Re: Storing dates By: Arno Welzel on Sun, 22 June 2014 19:56
		Re: Storing dates By: Mr Oldies on Mon, 23 June 2014 02:46
		Re: Storing dates By: Arno Welzel on Mon, 23 June 2014 06:11
		Re: Storing dates By: Mr Oldies on Mon, 23 June 2014 06:37
		Re: Storing dates By: Arno Welzel on Mon, 23 June 2014 09:10
		Re: Storing dates By: Evan Platt on Mon, 23 June 2014 13:50
		Re: Storing dates By: Mr Oldies on Mon, 23 June 2014 15:13
		Re: Storing dates By: Evan Platt on Mon, 23 June 2014 16:13
		Re: Storing dates By: Arno Welzel on Mon, 23 June 2014 20:33
		Re: Storing dates By: Mr Oldies on Mon, 23 June 2014 03:04
		Re: Storing dates By: Arno Welzel on Mon, 23 June 2014 06:12
		Re: Storing dates By: Geoff Muldoon on Mon, 23 June 2014 06:45
		Re: Storing dates By: Mr Oldies on Mon, 23 June 2014 11:58
		Re: Storing dates By: Jrgen Exner on Mon, 23 June 2014 16:50
		Re: Storing dates By: Christoph Michael Bec on Mon, 23 June 2014 17:02
		Re: Storing dates By: Geoff Muldoon on Tue, 24 June 2014 02:00
		Re: Storing dates By: Thomas 'PointedEars' on Tue, 24 June 2014 20:38
		Re: Storing dates By: Jrgen Exner on Sun, 22 June 2014 22:30
		Re: Storing dates By: Peter H. Coffin on Mon, 23 June 2014 01:10
		Re: Putting it all together By: Jrgen Exner on Sat, 21 June 2014 10:34
		Re: Putting it all together By: Denis McMahon on Sat, 21 June 2014 10:23
		Re: Putting it all together By: bill on Sat, 21 June 2014 11:03
		Re: Putting it all together By: Denis McMahon on Sat, 21 June 2014 15:11
		Re: Putting it all together By: Peter H. Coffin on Sat, 21 June 2014 15:57
		Re: Putting it all together By: Arno Welzel on Sun, 22 June 2014 06:45

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