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Cannot change column used in a foreign key constraint
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The type and definition of foreign key field and reference must be equal.
This means your foreign key disallows changing the type of your field.
One solution would be this:
LOCK TABLES
favorite_food WRITE,
person WRITE;
AL...
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...
What is the most efficient way of finding all the factors of a number in Python?
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The reduce(list.__add__, ...) is taking the little lists of [fac1, fac2] and joining them together in one long list.
The [i, n/i] for i in range(1, int(sqrt(n)) + 1) if n % i == 0 returns a pair of factors if the remainder when you divide n by the smaller one is zero (it doesn't need to check the...
AWS S3: how do I see how much disk space is using
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AWS Cloudwatch now has a metric for bucket size and number of objects that is updated daily. About time! aws.amazon.com/blogs/aws/…
– cudds
Jul 28 '15 at 23:13
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How to delete multiple values from a vector?
I have a vector like: a = c(1:10) and I need to remove multiple values, like: 2, 3, 5
8 Answers
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Get push notification while App in foreground iOS
...tificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void)
{
completionHandler([.alert, .badge, .sound])
}
iOS 10, Swift 2.3 :
@available(iOS 10.0, *)
func userNotificationCenter(center: UNUse...
What modern C++ libraries should be in my toolbox? [closed]
I've been out of the C++ game for about 10 years and I want to get back in and start on a commercial app. What libraries are in use these days?
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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...
How do I get the list of keys in a Dictionary?
I only want the Keys and not the Values of a Dictionary.
9 Answers
9
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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...