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MySQL Error 1215: Cannot add foreign key constraint
... Explosion Pill's answer covers the basics. You want to make sure to start from there. However, there are more, much more subtle cases to look out for:
For example, when you try to link up PRIMARY KEYs of different tables, make sure to provide proper ON UPDATE and ON DELETE options. E.g.:
...
PRIM...
Is ASCII code 7-bit or 8-bit?
...SCII-compatible means that regardless of context, single bytes with values from 0x00 through 0x7F encode the same characters that they would in ASCII. You don't want to have anything to do with a non-ASCII-compatible text encoding if you can possibly avoid it; naive programs expecting ASCII tend to...
What is the logic behind the “using” keyword in C++?
...lement, too confusing, or would contradict old code.
Here is an old paper from 2003 n1449. The rationale seems to be related to templates. Warning: there may be typos due to copying over from PDF.
First let’s consider a toy example:
template <typename T>
class MyAlloc {/*...*/};
template ...
Efficient list of unique strings C#
...)
orderList.Add(item);
When removing items, make sure to remove them from both. Thus, as long as you can be sure that nothing else added items to the list, you'll have an insertion-ordered unique set!
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No Multiline Lambda in Python: Why not?
... they could force the use of parentheses if you want to return a tuple from a lambda. IMO, this should have always been enforced to prevent such ambiguities, but oh well.
– mpen
Jul 28 '12 at 23:28
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redis-py : What's the difference between StrictRedis() and Redis()?
...tRedis.
2017-03-31
Here are the specifics of the backwards compatibility, from the github.com link cited:
In addition to the changes above, the Redis class, a subclass of StrictRedis, overrides several other commands to provide backwards compatibility with older versions of redis-py:
LREM: Order o...
Bootstrap 3 Flush footer to bottom. not fixed
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There is a simplified solution from bootstrap here (where you don't need to create a new class): http://getbootstrap.com/examples/sticky-footer-navbar/
When you open that page, right click on a browser and "View Source" and open the sticky-footer-navbar.c...
Android LocationClient class is deprecated but used in documentation
...an use LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient) from OnConnected
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How to get client's IP address using JavaScript?
...e of the returned data includes GeoLite data created by MaxMind, available from <a href=\\'http://www.maxmind.com\\'>http://www.maxmind.com</a>.",
"geoplugin_city": "Singapore",
"geoplugin_region": "Singapore (general)",
"geoplugin_areaCode": "0",
"geoplugin_dmaCode": "0",
"geo...
How can you do anything useful without mutable state?
...tand the syntax and underlying principles, then your eyes just glaze over. From your point of view, it looks as if I'm doing the same thing as an imperative language, but just setting up all kinds of boundaries to purposefully make programming more difficult. My point of view, you're just experienci...