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How to add column if not exists on PostgreSQL?
...statement:
DO $$
BEGIN
BEGIN
ALTER TABLE <table_name> ADD COLUMN <column_name> <column_type>;
EXCEPTION
WHEN duplicate_column THEN RAISE NOTICE 'column <column_name> already exists in <table_name>.';
END;
END;
$$
...
App Inventor 2 远程音频播放教程 - 网络音乐与语音播放 · App Inventor 2 中文网
...
音量控制
WebView播放网络音频
HTML文件（audio_player.html）
App Inventor积木块
实战案例：网络音乐播放器
功能
Sound组件（短音效）
Sound vs Player
常见问题
Q1: 播放网络音...
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...
How to do Base64 encoding in node.js?
...wered May 31 '11 at 2:46
onteria_onteria_
57.1k66 gold badges6363 silver badges6060 bronze badges
...
LINQ Select Distinct with Anonymous Types
...lt;T> : IEqualityComparer<T>
{
private Func<T, T, bool> _equals;
private Func<T, int> _hashCode;
public DelegateComparer(Func<T, T, bool> equals, Func<T, int> hashCode)
{
_equals= equals;
_hashCode = hashCode;
}
public bool Equ...
Can Flask have optional URL parameters?
...
Another way is to write
@user.route('/<user_id>', defaults={'username': None})
@user.route('/<user_id>/<username>')
def show(user_id, username):
pass
But I guess that you want to write a single route and mark username as optional? If that's the c...
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
...
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...
How do I add a linker or compile flag in a CMake file?
...ou want to add those flags (better to declare them in a constant):
SET(GCC_COVERAGE_COMPILE_FLAGS "-fprofile-arcs -ftest-coverage")
SET(GCC_COVERAGE_LINK_FLAGS "-lgcov")
There are several ways to add them:
The easiest one (not clean, but easy and convenient, and works only for compile flags,...
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...