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NULL values inside NOT IN clause
...t I thought were identical queries one using a not in where constraint and the other a left join . The table in the not in constraint had one null value (bad data) which caused that query to return a count of 0 records. I sort of understand why but I could use some help fully grasping the con...
Determine if Python is running inside virtualenv
...nside a virtual environment, sys.prefix points to the virtual environment, and sys.base_prefix is the prefix of the system Python the virtualenv was created from.
The above always works for Python 3 stdlib venv and for recent virtualenv (since version 20). Older versions of virtualenv used sys.real_...
OPTION (RECOMPILE) is Always Faster; Why?
...istics. This can be done by running the following:
EXEC sp_updatestats
And then recreating your execution plan. This will ensure that when your execution plan is created it will be using the latest information.
Adding OPTION(RECOMPILE) rebuilds the execution plan every time that your query exe...
How does “do something OR DIE()” work in PHP?
I'm writing a php app to access a MySQL database, and on a tutorial, it says something of the form
4 Answers
...
Which characters are valid in CSS class names/selectors?
...racter is a hyphen, the second character must2 be a letter or underscore, and the name must be at least 2 characters long.
-?[_a-zA-Z]+[_a-zA-Z0-9-]*
In short, the previous rule translates to the following, extracted from the W3C spec.:
In CSS, identifiers (including element names, classes, ...
What is the meaning of prepended double colon “::”?
...wered Nov 24 '10 at 16:27
Wyatt AndersonWyatt Anderson
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What are the underlying data structures used for Redis?
...every Redis operation you'll find the time complexity in the documentation and, if you have the set of operations and the time complexity, the only other thing you need is some clue about memory usage (and because we do many optimizations that may vary depending on data, the best way to get these la...
Cookies vs. sessions
...r the sake of creating a login system for my website, I read about cookies and sessions and their differences (cookies are stored in the user's browser and sessions on the server). At that time, I preferred cookies (and who does not like cookies?!) and just said: "who cares? I don't have any good de...
Generating v5 UUID. What is name and namespace?
I've read the man page, but I do not undestand what name and namespace are for.
3 Answers
...
“CASE” statement within “WHERE” clause in SQL Server 2008
...tatements like this:
WHERE (
(LEN('TestPerson') = 0
AND co.personentered = co.personentered
)
OR
(LEN('TestPerson') <> 0
AND co.personentered LIKE '%TestPerson')
)
Although, either way I'm not sure how great of a query plan...