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Can a foreign key be NULL and/or duplicate?
... exist first in a different table (the parent table). That is all an FK is by definition. Null by definition is not a value. Null means that we do not yet know what the value is.
Let me give you a real life example. Suppose you have a database that stores sales proposals. Suppose further that each ...
How do you get the “object reference” of an object in java when toString() and hashCode() have been
...says:
As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Jav...
EntityType has no key defined error
...[Key]) until I change the data types (I changed them to unsigned) and only byte works is there a reason I can't use unsigned values?
– Mihai Bratulescu
May 29 '14 at 9:31
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How to get form field's id in Django?
... imageUploader: {
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Transactions in REST?
... the Update or does it just do an Update and ignore the HTTP verb delete. By keeping verbs out of the endpoint you remove the confusion.
– Darrel Miller
Sep 29 '08 at 15:36
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Facebook API - How do I get a Facebook user's profile image through the Facebook API (without requir
...re" /> if you change between HTTP and HTTPS... the protocol is detected by the browser, and you won't get mixed content warnings on HTTPS.
– Chris Jacob
Nov 23 '11 at 1:45
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Postgres manually alter sequence
...e 22. false means that the next value would be the number provided, or 21. By default, setval will behave as if true was chosen. More details: postgresql.org/docs/9.6/static/functions-sequence.html
– Tom Mertz
Nov 7 '17 at 20:11
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When to use Comparable and Comparator
...ou want comparing behaviour different from the default (which is specified by Comparable) behaviour.
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How to get the selected index of a RadioGroup in Android
...oup.getCheckedRadioButtonId();
View radioButton = radioButtonGroup.findViewById(radioButtonID);
int idx = radioButtonGroup.indexOfChild(radioButton);
If the RadioGroup contains other Views (like a TextView) then the indexOfChild() method will return wrong index.
To get the selected RadioButton te...
Stop Mongoose from creating _id property for sub-document array items
... imageUploader: {
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