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MYSQL OR vs IN performance
...for future Googlers. Total count of returned results is 7264 out of 10000
SELECT * FROM item WHERE id = 1 OR id = 2 ... id = 10000
This query took 0.1239 seconds
SELECT * FROM item WHERE id IN (1,2,3,...10000)
This query took 0.0433 seconds
IN is 3 times faster than OR
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What is the difference between quiet NaN and signaling NaN?
...trtod and 7.22.1.3 "The strtod, strtof, and strtold functions" says:
A character sequence NAN or NAN(n-char-sequence opt ) is interpreted as a quiet
NaN, if supported in the return type, else like a subject sequence part that does not have
the expected form; the meaning of the n-char sequenc...
How to drop a table if it exists?
...
Is it correct to do the following?
IF EXISTS(SELECT *
FROM dbo.Scores)
DROP TABLE dbo.Scores
No. That will drop the table only if it contains any rows (and will raise an error if the table does not exist).
Instead, for a permanent table you can use
I...
How to Join to first row
...
SELECT Orders.OrderNumber, LineItems.Quantity, LineItems.Description
FROM Orders
JOIN LineItems
ON LineItems.LineItemGUID =
(
SELECT TOP 1 LineItemGUID
FROM LineItems
W...
Checkbox for nullable boolean
...ents your null, whatever the semantics of null means. You could use a <select><option> drop down list to save real estate, but the user has to click twice and the choices aren't nearly as instantaneously clear.
1 0 null
True False Not Set
Yes No Undecided
Male Fema...
Alternative to itoa() for converting integer to string C++? [duplicate]
...s pretty well.
#include <boost/lexical_cast.hpp>
int main(int argc, char** argv) {
std::string foo = boost::lexical_cast<std::string>(argc);
}
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How to express a NOT IN query with ActiveRecord/Rails?
...rums, lambda { |forums| { :conditions => ['forum_id not in (?)', forums.select(&:id).join(',')] }
# in your controller
Topic.not_in_forums(@forums)
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Difference between 'new operator' and 'operator new'?
...ething like your own container, you can call operator new directly, like:
char *x = static_cast<char *>(operator new(100));
It's also possible to overload operator new either globally, or for a specific class. IIRC, the signature is:
void *operator new(size_t);
Of course, if you overloa...
Ruby, remove last N characters from a string?
What is the preferred way of removing the last n characters from a string?
13 Answers
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Difference between Select Unique and Select Distinct
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SELECT UNIQUE is old syntax supported by Oracle's flavor of SQL. It is synonymous with SELECT DISTINCT.
Use SELECT DISTINCT because this is standard SQL, and SELECT UNIQUE is non-standard, and in database brands other than ...