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Add unique constraint to combination of two columns
...g an exception (exceptions are expensive).
http://www.sqlperformance.com/2012/08/t-sql-queries/error-handling
http://www.mssqltips.com/sqlservertip/2632/checking-for-potential-constraint-violations-before-entering-sql-server-try-and-catch-logic/
If you want to prevent exceptions from bubbling up ...
How can I add a help method to a shell script?
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here's an example for bash:
usage="$(basename "$0") [-h] [-s n] -- program to calculate the answer to life, the universe and everything
where:
-h show this help text
-s set the seed value (default: 42)"
seed=42
while getopts ':hs:' option; do
case "$option" i...
What is the Python equivalent of static variables inside a function?
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703
A bit reversed, but this should work:
def foo():
foo.counter += 1
print "Counter is %d...
How to install Java SDK on CentOS?
...n you read this, the lastest available version may be different.
java-1.7.0-openjdk.x86_64
The above package alone will only install JRE. To also install javac and JDK, the following command will do the trick:
$ yum install java-1.7.0-openjdk*
These packages will be installing (as well as thei...
Cartesian product of x and y array points into single array of 2D points
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kennytmkennytm
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Overlaying histograms with ggplot2 in R
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Your current code:
ggplot(histogram, aes(f0, fill = utt)) + geom_histogram(alpha = 0.2)
is telling ggplot to construct one histogram using all the values in f0 and then color the bars of this single histogram according to the variable utt.
What you want instead is...
Why does (1 in [1,0] == True) evaluate to False?
...arison operator chaining here. The expression is translated to
(1 in [1, 0]) and ([1, 0] == True)
which is obviously False.
This also happens for expressions like
a < b < c
which translate to
(a < b) and (b < c)
(without evaluating b twice).
See the Python language documentat...
How to find the key of the largest value hash?
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230
This will return max hash key-value pair depending on the value of hash elements:
def largest_h...
How do you find the sum of all the numbers in an array in Java?
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In java-8 you can use streams:
int[] a = {10,20,30,40,50};
int sum = IntStream.of(a).sum();
System.out.println("The sum is " + sum);
Output:
The sum is 150.
It's in the package java.util.stream
import java.util.stream.*;
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'parent.relativePath' points at my com.mycompany:MyProject instead of org.apache:apache - Why?
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260
Add an empty <relativePath> to <parent> so that it resolves the parent pom from the ...