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How to find gaps in sequential numbering in mysql?
...performance.
The (not as fast as possible) answer
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 t...
Given a class, see if instance has method (Ruby)
I know in Ruby that I can use respond_to? to check if an object has a certain method.
12 Answers
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Intersection and union of ArrayLists in Java
Are there any methods to do so? I was looking but couldn't find any.
23 Answers
23
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What is the difference between varchar and nvarchar?
...data. A varchar column is restricted to an 8-bit codepage. Some people think that varchar should be used because it takes up less space. I believe this is not the correct answer. Codepage incompatabilities are a pain, and Unicode is the cure for codepage problems. With cheap disk and memory nowadays...
What is LINQ and what does it do? [closed]
What is LINQ? I know it's for databases, but what does it do?
7 Answers
7
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When should I use Memcache instead of Memcached?
...es named memcache and memcached . What is the difference and how do you know which one to use? Is one outdated? It seems that memcached offers more methods so I would assume that means it has had the most development - but it also seems to require external C/C++ libraries so I'm not sure if I c...
Display Animated GIF
...ndroid.graphics.Movie class.
This is not too much documented, but is in SDK Reference. Moreover, it is used in Samples in ApiDemos in BitmapDecode example with some animated flag.
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How do I determine if a port is open on a Windows server? [closed]
... that you're trying to use:
On the server itself, use netstat -an to check to see which ports are listening.
From outside, just use telnet host port (or telnet host:port on Unix systems) to see if the connection is refused, accepted, or timeouts.
On that latter test, then in general:
connectio...
What does “while True” mean in Python?
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while True means loop forever. The while statement takes an expression and executes the loop body while the expression evaluates to (boolean) "true". True always evaluates to boolean "true" and thus executes the loop body indefinitely. It's an idiom that you'll just get used to...
Create a date from day month and year with T-SQL
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