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How to add column if not exists on PostgreSQL?
...statement:
DO $$
BEGIN
BEGIN
ALTER TABLE <table_name> ADD COLUMN <column_name> <column_type>;
EXCEPTION
WHEN duplicate_column THEN RAISE NOTICE 'column <column_name> already exists in <table_name>.';
END;
END;
$$
...
Does Swift support reflection?
...Have a look the answer stackoverflow.com/a/25345461/292145 to find out how _stdlib_getTypeName can help.
– Klaas
Aug 17 '14 at 1:14
1
...
Eclipse returns error message “Java was started but returned exit code = 1”
...ter -vmargs is passed directly to the JVM.
-vm
c:/wherever/java/jdk1.6.0_21/jre/bin/server/jvm.dll
-vmargs...
...to your eclipse.ini file, pointing to the JDK you want to use, and check that the required Java version is at least as new as your JDK. This is the path for a Windows system. More o...
error C2664: “std::list::list(const std::allocator &)”: 不能将参数 1...
...转换为“const std::allocator &”错误日志：error C2664: std::list<_Ty>::list(const std::allocator<_Ty> &): 不能将参数 1 从std::vector<_Ty>转换为const std::...错误日志：
error C2664: “std::list<_Ty>::list(const std::allocator<_Ty> &)”: 不能将参数 1 从
“std::vect...
Should I URL-encode POST data?
...ould read the documentation here.
Here's the relevant information:
CURLOPT_POST
TRUE to do a regular HTTP POST.
This POST is the normal application/x-www-form-urlencoded kind, most commonly used by HTML forms.
CURLOPT_POSTFIELDS
The full data to post in a HTTP "POST" operation. To post a file, prep...
What are rvalues, lvalues, xvalues, glvalues, and prvalues?
... three: lvalue, xvalue, prvalue. A Venn diagram would look like this:
______ ______
/ X \
/ / \ \
| l | x | pr |
\ \ / /
\______X______/
gl r
Examples with functions:
int prvalue();
int& lvalue();
int&& xvalue();
But al...
Is there a short contains function for lists?
..., you may also be interested to know that what in does is to call the list.__contains__ method, that you can define on any class you write and can get extremely handy to use python at his full extent.
A dumb use may be:
>>> class ContainsEverything:
def __init__(self):
retu...
Node.js get file extension
...inted out, and not write your own. More info: nodejs.org/api/path.html#path_path_extname_p
– xentek
Feb 23 '14 at 6:20
...
How to run a program without an operating system?
...125\252' > main.img
sudo apt-get install qemu-system-x86
qemu-system-x86_64 -hda main.img
Outcome:
Note that even without doing anything, a few characters are already printed on the screen. Those are printed by the firmware, and serve to identify the system.
And on the T430 we just get a blank ...
Is there a way to make mv create the directory to be moved to if it doesn't exist?
... this one-liner (in bash):
mkdir --parents ./some/path/; mv yourfile.txt $_
Breaking that down:
mkdir --parents ./some/path
creates the directory (including all intermediate directories), after which:
mv yourfile.txt $_
moves the file to that directory ($_ expands to the last argument passe...