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When and why are database joins expensive?
...s back to mitigating the size of the working set. Joins involving properly selected keys with correctly set up indexes are cheap, not expensive, because they allow significant pruning of the result before the rows are materialised.
Materialising the result involves bulk disk reads which are the mo...
Finding the id of a parent div using Jquery
...the result like this $(parent[0]).attr('id') after I did like a few parent selectors.
– Piotr Kula
Nov 7 '14 at 22:02
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Simulator error FBSSystemServiceDomain code 4
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Go to the iOS Simulator menu and select Reset Content and Settings.
Alternatively, you could quit and reopen the Simulator.
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关于php的socket初探 - PHP - 清泛IT论坛，有思想、有深度
...连接的模型都应该被称为多路复用，目前比较常用的有 select/poll/epoll/kqueue 这些 IO 模型（目前也有像 Apache 这种每个连接用单独的进程/线程来处理的 IO 模型，但是效率相对比较差，也很容易出问题，所以暂时不做介绍了）。在...
Proper Linq where clauses
...cate are combined and only one iterator is involed. Look atEnumerable.WhereSelectEnumerableIterator.
– Cybermaxs
Apr 4 '13 at 12:46
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'0000-00-00 00:00:00' can not be represented as java.sql.Timestamp error
...o update the values, or while these modifications take place, you can do a select using a case/when.
SELECT CASE ModificationDate WHEN '0000-00-00 00:00:00' THEN '1970-01-01 01:00:00' ELSE ModificationDate END AS ModificationDate FROM Project WHERE projectId=1;
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What is the equivalent of bigint in C#?
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I just had a script that returned the primary key of an insert and used a
SELECT @@identity
on my bigint primary key, and I get a cast error using long - that was why I started this search. The correct answer, at least in my case, is that the type returned by that select is NUMERIC which equates t...
What's the recommended approach to resetting migration history using Django South?
...ps, so make sure you either run the other two lines for all apps or delete selectively).
The convert_to_south call at the end makes a new migration and fake-applies it (since your database already has the corresponding tables). There's no need to drop all the app tables during the process.
He...
How do I set default terminal to terminator? [closed]
...n a terminal, try
sudo update-alternatives --config x-terminal-emulator
Select the desired terminal from the list of alternatives.
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Why use a READ UNCOMMITTED isolation level?
...on. This option has the same effect as setting NOLOCK on all tables in all SELECT statements in a transaction. This is the least restrictive of the four isolation levels.
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