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ERROR 1452: Cannot add or update a child row: a foreign key constraint fails
...relationships involve a parent table that holds the
central data values, and a child table with identical values pointing
back to its parent. The FOREIGN KEY clause is specified in the child
table.
It will reject any INSERT or UPDATE operation that attempts to create
a foreign key value...
What is the proper way to format a multi-line dict in Python?
...uld use a similar but not identical format as your format 3. Here is mine, and why.
my_dictionary = { # Don't think dict(...) notation has more readability
"key1": 1, # Indent by one press of TAB (i.e. 4 spaces)
"key2": 2, # Same indentation scale as above
"key3": 3, # Keep this final c...
Does MongoDB's $in clause guarantee order
...the results
{ "$sort": { "weight": 1 } }
])
So that would be the expanded form. What basically happens here is that just as the array of values is passed to $in you also construct a "nested" $cond statement to test the values and assign an appropriate weight. As that "weight" value reflects t...
How can I create a copy of an object in Python?
... you can use the copy.deepcopy() function.
For more details about shallow and deep copying please refer to the other answers to this question and the nice explanation in this answer to a related question.
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How do you get assembler output from C/C++ source in gcc?
... the preprocessor (cpp) over helloworld.c, perform the initial compilation and then stop before the assembler is run.
By default this will output a file helloworld.s. The output file can be still be set by using the -o option.
gcc -S -o my_asm_output.s helloworld.c
Of course this only works if y...
How to show only next line after the matched one?
Thanks to this command for every line that has 'blah' in it, I get the output of the line that contains 'blah' and the next line that follows in the logfile. It might be a simple one but I can't find a way to omit the line that has 'blah' and only show next line in the output.
...
Unnecessary curly braces in C++?
...ould not do this until C99. :)
Since C++ has destructors, it can also be handy to have resources (files, mutexes, whatever) automatically released as the scope exits, which can make things cleaner. This means you can hold on to some shared resource for a shorter duration than you would if you grabb...
What is the use for IHttpHandler.IsReusable?
I'm writing a IHttpHandler and I'll need to implement a IsReusable property. When I look at the MSDN documentation it says:
...
How to detect the screen resolution with JavaScript?
...with the device pixel ratio: window.screen.width * window.devicePixelRatio and window.screen.height * window.devicePixelRatio. This will also work on desktops, which will have a ratio of 1.
And from Ben in another answer:
In vanilla JavaScript, this will give you the AVAILABLE width/height:
window...
Get value of a string after last slash in JavaScript
I am already trying for over an hour and cant figure out the right way to do it, although it is probably pretty easy:
10 An...