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Why does comparing strings using either '==' or 'is' sometimes produce a different result?
...s and dynamic
programming language runtimes) that
rely heavily on hash tables with
string keys. Without interning,
checking that two different strings
are equal involves examining every
character of both strings. This is
slow for several reasons: it is
inherently O(n) in the length o...
Select statement to find duplicates on certain fields
...ltiple records, you can use..
select field1,field2,field3, count(*)
from table_name
group by field1,field2,field3
having count(*) > 1
Check this link for more information on how to delete the rows.
http://support.microsoft.com/kb/139444
There should be a criterion for deciding how you defi...
Equals(=) vs. LIKE
...rmance:
A personal example using mysql 5.5: I had an inner join between 2 tables, one of 3 million rows and one of 10 thousand rows.
When using a like on an index as below(no wildcards), it took about 30 seconds:
where login like '12345678'
using 'explain' I get:
When using an '=' on the s...
Thread-safe List property
...em.ServiceModel.dll (which is part of the client profile but not of the portable class library).
Hope that helps.
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How to vertically align into the center of the content of a div with defined width/height?
...I have found you have four options:
Version 1: Parent div with display as table-cell
If you do not mind using the display:table-cell on your parent div, you can use of the following options:
.area{
height: 100px;
width: 100px;
background: red;
margin:10px;
text-align: center;
...
sqlite alter table add MULTIPLE columns in a single statement
Is it possible to alter table add MULTIPLE columns in a single statement in sqlite?
The following would not work.
4 Answers...
What's the difference between django OneToOneField and ForeignKey?
....title
Run python manage.py syncdb to execute the sql code and build the tables for your app in your database. Then use python manage.py shell to open a python shell.
Create the Reporter object R1.
In [49]: from thepub.models import Reporter, Article
In [50]: R1 = Reporter(first_name='Rick')
I...
Importance of varchar length in MySQL table
I have a MySQL table where rows are inserted dynamically. Because I can not be certain of the length of strings and do not want them cut off, I make them varchar(200) which is generally much bigger than I need. Is there a big performance hit in giving a varchar field much more length than necessar...
How to re-sync the Mysql DB if Master and slave have different database incase of Mysql replication?
...aster-slave replication from scratch:
At the master:
RESET MASTER;
FLUSH TABLES WITH READ LOCK;
SHOW MASTER STATUS;
And copy the values of the result of the last command somewhere.
Without closing the connection to the client (because it would release the read lock) issue the command to get a d...
Detect Windows version in .net
...nment is running in, check out this library.
Important note: if your executable assembly manifest doesn't explicitly state that your exe assembly is compatible with Windows 8.1 and Windows 10.0, System.Environment.OSVersion will return Windows 8 version, which is 6.2, instead of 6.3 and 10.0! Sourc...