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How to find gaps in sequential numbering in mysql?
...r
Here's version that works on table of any size (not just on 100 rows):
SELECT (t1.id + 1) as gap_starts_at,
(SELECT MIN(t3.id) -1 FROM arrc_vouchers t3 WHERE t3.id > t1.id) as gap_ends_at
FROM arrc_vouchers t1
WHERE NOT EXISTS (SELECT t2.id FROM arrc_vouchers t2 WHERE t2.id = t1.id + ...
C++ STL Vectors: Get iterator from index?
... legal to do this folowing, according to me:
int main()
{
void foo(const char *);
sdt::vector<char> vec;
vec.push_back('h');
vec.push_back('e');
vec.push_back('l');
vec.push_back('l');
vec.push_back('o');
vec.push_back('/0');
foo(&vec[0]);
}
Of course, either foo must not copy the ad...
.net implementation of bcrypt
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Article moved: chargen.matasano.com/chargen/2007/9/7/enough-with-the-rainbow- tables-what-you-need-to-know-about-s.html
– Code Silverback
May 7 '12 at 13:46
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MySQL select 10 random rows from 600K rows fast
How can I best write a query that selects 10 rows randomly from a total of 600k?
26 Answers
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On select change, get data attribute value
...
You need to find the selected option:
$(this).find(':selected').data('id')
or
$(this).find(':selected').attr('data-id')
although the first method is preferred.
shar...
Is multiplication and division using shift operators in C actually faster?
... back, I benchmarked two
versions of my hashing algorithm:
unsigned
hash( char const* s )
{
unsigned h = 0;
while ( *s != '\0' ) {
h = 127 * h + (unsigned char)*s;
++ s;
}
return h;
}
and
unsigned
hash( char const* s )
{
unsigned h = 0;
while ( *s != '\0' ...
What is the difference between CHARACTER VARYING and VARCHAR in PostgreSQL?
John uses CHARACTER VARYING in the places where I use VARCHAR .
I am a beginner, while he is an expert.
This suggests me that there is something which I do not know.
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How to select unique records by SQL
When I perform "SELECT * FROM table" I got results like below:
8 Answers
8
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When should I use cross apply over inner join?
...APPLY works better on things that have no simple JOIN condition.
This one selects 3 last records from t2 for each record from t1:
SELECT t1.*, t2o.*
FROM t1
CROSS APPLY
(
SELECT TOP 3 *
FROM t2
WHERE t2.t1_id = t1.id
ORDER BY
t2.ran...
What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
The "N+1 selects problem" is generally stated as a problem in Object-Relational mapping (ORM) discussions, and I understand that it has something to do with having to make a lot of database queries for something that seems simple in the object world.
...