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How to add column if not exists on PostgreSQL?
...statement:
DO $$
BEGIN
BEGIN
ALTER TABLE <table_name> ADD COLUMN <column_name> <column_type>;
EXCEPTION
WHEN duplicate_column THEN RAISE NOTICE 'column <column_name> already exists in <table_name>.';
END;
END;
$$
...
Apache not starting on MAMP Pro
.... Go to bin -> apache2 -> bin.
Then rename the file from envvars to _envvars.
I also came across another problem of it not working correctly. Make sure the ports are Apache defaults, NOT MAMP defaults (port 80 etc). If it works straight away, this should not apply to you.
...
HAXM 安装/启动失败？ - App Inventor 2 离线版 - 清泛IT社区，为创新赋能！
报错如下：
引用: emulator: Android emulator version 30.3.5.0 (build_id 7033400) (CL:N/A)
127.0.0.1 - - [01/Apr/2025 16:55:37] "GET /echeck/ HTTP/1.1" 200 39
handleCpuAcceleration: feature check for hvf
emulator: ERROR: x86_64 emulation currently requires hardware acceleration!
C...
Escape angle brackets in a Windows command prompt
... containing angle brackets (< and >) to a file on a Windows machine. Basically what I want to do is the following:
echo some string < with angle > brackets >>myfile.txt
...
How do I force Postgres to use a particular index?
...of why and what you can do instead can be found here. The reasons are basically that it's a performance hack that tends to cause more problems later down the line as your data changes, whereas PostgreSQL's optimizer can re-evaluate the plan based on the statistics. In other words, what might be a go...
When to use IMG vs. CSS background-image?
...ng icon. This ensures that the meaning of the image can be communicated in all user-agents, including screen readers.
Pragmatic uses of IMG
Use IMG plus alt attribute if the image
is part of the content such as a logo or diagram or person (real person, not stock photo people).
—sanchothefat...
Force to open “Save As…” popup open at text link click for PDF in HTML
... the time of this comment, I've tested it on Chrome, Opera, Edge, Mozilla. All latest. Is working on all except on Mozilla.
– S.I.
Sep 29 '17 at 5:07
7
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What's the idiomatic syntax for prepending to a short python list?
... @MattM. If you insert at the front of a list, python has to move all the other items one space forwards, lists can't "make space at the front". collections.deque (double ended queue) has support for "making space at the front" and is much faster in this case.
– fejfo
...
get size of json object
... check the size i.e. like that:
var data = {one : 1, two : 2, three : 3};
_.size(data);
//=> 3
_.keys(data);
//=> ["one", "two", "three"]
_.keys(data).length;
//=> 3
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What should be in my .gitignore for an Android Studio project?
...kbox and mark the "use default gradle wrapper (recommended)" radio button. All paths are now relative as @George suggested.
Updated answer according to @128KB attached source and @Skela suggestions
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