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How to add column if not exists on PostgreSQL?
Question is simple. How to add column x to table y , but only when x column doesn't exist ? I found only solution here how to check if column exists.
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stdlib and colored output in C
...'t bother with libraries, the code is really simple.
More info is here.
Example in C:
#include <stdio.h>
#define ANSI_COLOR_RED "\x1b[31m"
#define ANSI_COLOR_GREEN "\x1b[32m"
#define ANSI_COLOR_YELLOW "\x1b[33m"
#define ANSI_COLOR_BLUE "\x1b[34m"
#define ANSI_COLOR_MAGENTA "\x1b[...
In Java, what does NaN mean?
...meters
that cause the operation to produce
some undefined result. For example,
0.0 divided by 0.0 is arithmetically undefined. Taking the square root of a
negative number is also undefined.
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how to remove untracked files in Git?
I'm working on a branch, say "experimental" branch which I branch out from my master branch.Then, I generate a user model in experimental branch, but does not add them to index yet.
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How to install the Raspberry Pi cross compiler on my Linux host machine?
...ls.git
You wanted to use the following of the 3 ones, gcc-linaro-arm-linux-gnueabihf-raspbian, if I did not read wrong.
Go into your home directory and add:
export PATH=$PATH:$HOME/raspberrypi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin
to the end of the file named ~/.bashrc
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Apache Prefork vs Worker MPM
...tion at a time// here connection means single user or single request? pls explain
– user1844933
Jun 25 '19 at 7:18
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What is the easiest way to push an element to the beginning of the array?
...in use:
irb>> a = [ 0, 1, 2]
=> [0, 1, 2]
irb>> a.unshift('x')
=> ["x", 0, 1, 2]
irb>> a.inspect
=> "["x", 0, 1, 2]"
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Replace all non-alphanumeric characters in a string
...a standard character or number such as (a-z or 0-9) with an asterisk. For example, "h^&ell`.,|o w]{+orld" is replaced with "h*ell*o*w*orld". Note that multiple characters such as "^&" get replaced with one asterisk. How would I go about doing this?
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What are bitwise shift (bit-shift) operators and how do they work?
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The bit shifting operators do exactly what their name implies. They shift bits. Here's a brief (or not-so-brief) introduction to the different shift operators.
The Operators
>> is the arithmetic (or signed) right shift operator.
>>> is t...
How do I revert all local changes in Git managed project to previous state?
..., do this:
git checkout .
If you want to revert changes made to the index (i.e., that you have added), do this. Warning this will reset all of your unpushed commits to master!:
git reset
If you want to revert a change that you have committed, do this:
git revert <commit 1> <commit 2&...