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@UniqueConstraint annotation in Java
...name;
The @UniqueConstraint annotation is for annotating multiple unique keys at the table level, which is why you get an error when applying it to a field.
References (JPA TopLink):
@UniqueConstraint
@Column
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How do I see active SQL Server connections?
... Server connections, and the related information of all the connections, like from which IP address, connect to which database or something.
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How to convert / cast long to String?
...'t want to get a 4-letter "null" string, you might use Objects.toString, like: String s = Objects.toString(date, null);
EDIT:
You reverse it using Long l = Long.valueOf(s); but in this direction you need to catch NumberFormatException
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How can I find unused images and CSS styles in a website? [closed]
...t has had an option to spider the whole site. Version 3.01 should could work with newer versions of Firefox.
http://www.brothercake.com/dustmeselectors/
And here's another option:
https://addons.mozilla.org/en-US/firefox/addon/css-usage/
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Trimming a huge (3.5 GB) csv file to read into R
...that has a lot of detail and incomplete rows (leading Access and SQL to choke). It's county level data set broken into segments, sub-segments, and sub-sub-segments (for a total of ~200 factors) for 40 years. In short, it's huge, and it's not going to fit into memory if I try to simply read it.
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How do you sort a dictionary by value?
I often have to sort a dictionary, consisting of keys & values, by value. For example, I have a hash of words and respective frequencies, that I want to order by frequency.
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How to check if a String contains only ASCII?
...c) returns true if the character is a letter. But is there a way to quickly find if a String only contains the base characters of ASCII?
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How to grep (search) committed code in the Git history
...ent (i.e., actual lines of source, as opposed to commit messages and the like), you need to do:
git grep <regexp> $(git rev-list --all)
git rev-list --all | xargs git grep <expression> will work if you run into an "Argument list too long" error.
If you want to limit the search to som...
Is there a version control system for database structure changes?
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In Ruby on Rails, there's a concept of a migration -- a quick script to change the database.
You generate a migration file, which has rules to increase the db version (such as adding a column) and rules to downgrade the version (such as removing a column). Each migration is numbered,...
How do I escape a single quote in SQL Server?
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