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What's the difference between identifying and non-identifying relationships?
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An identifying relationship is when the existence of a row in a child table depends on a row in a parent table. This may be confusing because it's common practice these days to create a pseudokey for a child table, but not make...
Why can't enum's constructor access static fields?
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The constructor is called before the static fields have all been initialized, because the static fields (including those representing the enum values) are initialized in textual order, and the enum values always come before the other fields. No...
SQL UPDATE SET one column to be equal to a value in a related table referenced by a different column
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update q
set q.QuestionID = a.QuestionID
from QuestionTrackings q
inner join QuestionAnswers a
on q.AnswerID = a.AnswerID
where q.QuestionID is null -- and other conditions you might want
I recommend to check what the result set to update is befo...
background function in Python
...hem is. I've got a function that downloads the image needed and saves it locally. Right now it's run inline with the code that displays a message to the user, but that can sometimes take over 10 seconds for non-local images. Is there a way I could call this function when it's needed, but run it in ...
HTML entity for the middle dot
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It's called a middle dot: ·
HTML entities:
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·
·
In CSS:
\00B7
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improve this answer...
Static function variables in Swift
I'm trying to figure out how to declare a static variable scoped only locally to a function in Swift.
4 Answers
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selecting unique values from a column
...o if you want the whole record, the DISTINCT is worthless (unless it is an id field, and you can do a second query where id IN that list). Good news, though, if you have multiple duplicate results as a result of a JOIN you can do a GROUP BY and get the full results filtered.
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mysql update column with value from another table
... UPDATE participants_registrations INNER JOIN participants ON participants.id = participants_registrations.participantId INNER JOIN registrations ON registrations.id = participants_registrations.registrationId LEFT JOIN groups ON (groups.id = registrations.groupId) SET registrations.groupId = g...
Why is there no Constant feature in Java?
...hat an object is immutable when accessed through a special kind of pointer called a const-pointer When in Java, in places where I'd normally want to return a const-pointer, I instead return a reference with an interface type containing only methods that shouldn't have side effects. Unfortunately, ...
Difference between except: and except Exception as e: in Python
... print e.message, e.args
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>>> catch()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 3, in catch
BaseException
Which a bare except does:
>>> def catch():
... try:
... raise BaseException()
... ...