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In Postgresql, force unique on combination of two columns
...I like the suggestion of a primary key over unique here, because we do not allow NULL values in this case. From the PostgeSQL docs: "Note that a unique constraint does not, by itself, provide a unique identifier because it does not exclude null values.)" postgresql.org/docs/8.1/static/ddl-constraint...
Performance - Date.now() vs Date.getTime()
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These things are the same (edit semantically; performance is a little better with .now()):
var t1 = Date.now();
var t2 = new Date().getTime();
However, the time value from any already-created Date instance is frozen at the time of its construction (or at whateve...
Can anybody find the TFS “Unshelve” option in Visual Studio 2012?
..."Find Shelvesets", then right click on the shelve you want to unshelve, finally "Unshelve".
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How can I control the width of a label tag?
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You can either give class name to all label so that all can have same width :
.class-name { width:200px;}
Example
.labelname{ width:200px;}
or you can simple give rest of label
label { width:200px; display: inline-block;}
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Commit changes to a different branch than the currently checked out branch with subversion
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I recommend not to choose the root folder with all the irrelevant sub-folders which are not subject to be modified in the branch. Later it will be easier to merge the (smaller) branch back to trunk.
– J Pollack
Mar 5 '15 at 9:24
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How to manually deprecate members
...ike Objective-C, Swift has no preprocessor, so is there still a way to manually deprecate members of a class?
4 Answers
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In C#, how can I create a TextReader object from a string (without writing to disk)
...text into a webpage. The Fast CSV reader requires a TextReader object, and all I have is a string. What's the best way to convert a string into a TextReader object on the fly?
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What is the difference between exit and return? [duplicate]
...hat is difference between return and exit statement in C programming when called from anywhere in a C program?
4 Answers
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Pass a data.frame column name to a function
...l_name,col1,col2){
df$col_name <- df$col1 + df$col2
df
}
#Call foo() like this:
foo(dat,z,x,y)
The problem here is that df$col1 doesn't evaluate the expression col1. It simply looks for a column in df literally called col1. This behavior is described in ?Extract under the secti...
SELECT * WHERE NOT EXISTS
...r original query will always return nothing unless there are no records at all in eotm_dyn, in which case it will return everything.
Assuming these tables should be joined on employeeID, use the following:
SELECT *
FROM employees e
WHERE NOT EXISTS
(
SELECT null
...