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how to emulate “insert ignore” and “on duplicate key update” (sql merge) with postgresql?
Some SQL servers have a feature where INSERT is skipped if it would violate a primary/unique key constraint. For instance, MySQL has INSERT IGNORE .
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Reshaping data.frame from wide to long format
...ert my data.frame from a wide table to a long table.
At the moment it looks like this:
9 Answers
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Can javax.persistence.Query.getResultList() return null?
...pecification says nothing about it. But Java Persistence with Hibernate book, 2nd edition, says:
If the query result is empty, a null is returned
Hibernate JPA implementation (Entity Manager) return null when you call query.getResultList() with no result.
UPDATE
As pointed out by some users,...
Large Numbers in Java
... for numbers with decimal digits. Both classes are defined in java.math package.
Example:
BigInteger reallyBig = new BigInteger("1234567890123456890");
BigInteger notSoBig = new BigInteger("2743561234");
reallyBig = reallyBig.add(notSoBig);
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How do I find and view a TFS changeset by comment text?
... but I don't see a simple way in the Source Control Explorer to do this task?
11 Answers
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1052: Column 'id' in field list is ambiguous
...mended approach -- why type more than you have to?
Why Do These Queries Look Different?
Secondly, my answers use ANSI-92 JOIN syntax (yours is ANSI-89). While they perform the same, ANSI-89 syntax does not support OUTER joins (RIGHT, LEFT, FULL). ANSI-89 syntax should be considered deprecated, the...
Remove file from SVN repository without deleting local copy
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svn delete --keep-local the_file
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How do I write JSON data to a file?
...tual JSON part - data is a dictionary and not yet JSON-encoded. Write it like this for maximum compatibility (Python 2 and 3):
import json
with open('data.json', 'w') as f:
json.dump(data, f)
On a modern system (i.e. Python 3 and UTF-8 support), you can write a nicer file with
import json
wi...
iOS Detect 3G or WiFi
...y reachabilityForInternetConnection];
[reachability startNotifier];
NetworkStatus status = [reachability currentReachabilityStatus];
if(status == NotReachable)
{
//No internet
}
else if (status == ReachableViaWiFi)
{
//WiFi
}
else if (status == ReachableViaWWAN)
{
//3G
}
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How to get the ASCII value of a character
...ould get the int value
of the char. And in case you want to
convert back after playing with the
number, function chr() does the trick.
>>> ord('a')
97
>>> chr(97)
'a'
>>> chr(ord('a') + 3)
'd'
>>>
In Python 2, there is also the unichr function, returning...