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Add new column with foreign key constraint in one command
...the DBMS. Some DBMS allow you to combine ALTER table operations separated by commas. For example...
Informix syntax:
ALTER TABLE one
ADD two_id INTEGER,
ADD CONSTRAINT FOREIGN KEY(two_id) REFERENCES two(id);
The syntax for IBM DB2 LUW is similar, repeating the keyword ADD but (if I read...
How do I calculate square root in Python?
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What you're seeing is integer division. To get floating point division by default,
from __future__ import division
Or, you could convert 1 or 2 of 1/2 into a floating point value.
sqrt = x**(1.0/2)
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The command rbenv install is missing
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The install command is not embedded into rbenv, it comes from the ruby-build plugin. You can install it using the command:
git clone https://github.com/rbenv/ruby-build.git "$(rbenv root)"/plugins/ruby-build
On Mac OS X you can install it through homebrew:
brew install ruby-build
On Deb...
How to get current date in jquery?
...complex one, because it must deal with months & days being represented by numbers less than 10 (meaning the strings will have one char instead of two). See this jsfiddle for comparison.
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last day of month calculation
...uired date before calling getActualMaximum. The first date can be obtained by getActualMinimum()
– AlexR
Feb 22 '12 at 16:14
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how to convert binary string to decimal?
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parseInt() with radix is a best solution (as was told by many):
But if you want to implement it without parseInt, here is an implementation:
function bin2dec(num){
return num.split('').reverse().reduce(function(x, y, i){
return (y === '1') ? x + Math.pow(2, i) : x;...
jquery select change event get selected option
...with this.options[ this.options.selectedIndex ]. Mozilla says is supported by Firefox from 26, IE No support.
– Bernhard Döbler
Dec 14 '16 at 8:36
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How to check if a json key exists?
...uld also
use optString instead of getString:
Returns the value mapped by name if it exists, coercing it if
necessary. Returns the empty string if no such mapping exists
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git-svn not a git command?
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I had the same error under Cygwin 1.7. It was solved by installing the git-svn package with Cygwin setup.
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follow
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The way to check a HDFS directory's size?
... than the individual files. Without the -s option, the calculation is done by going 1-level deep from the given path.
The -h option will format file sizes in a human-readable fashion (e.g 64.0m instead of 67108864)
The -v option will display the names of columns as a header line.
The -x option will ...