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扒了一下源码，ESP8285接入App Inventor有4种玩法，第3种最香 - AI 助手 - ...
...时双向通信，零新开发。
缺点：ESP8285配网后才能知道IP，每次换网络要重新设置。
方案3：MQTT（生产环境最推荐）
通过MQTT Broker中转，ESP8285和App Inventor都连同一个Broker。
ESP8285端用PubSubClient库（Arduino标准库），App端用f...
How do I match any character across multiple lines in a regular expression?
...o_mod_m (source).
As for oracle (it is POSIX based), use n option (demo): select regexp_substr('abcde' || chr(10) ||' fghij<Foobar>', '(.*)<Foobar>', 1, 1, 'n', 1) as results from dual
POSIX-based engines:
A mere . already matches line breaks, no need to use any modifiers, see bas...
Detailed 500 error message, ASP + IIS 7.5
...rs to browser", and click "Apply".
Under "Error Pages" on the home screen select "500", then "Edit feature settings" and select "Detailed Errors".
Note that the same steps apply for IIS 8.0 (Windows Server 2012).
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...
How do you discover model attributes in Rails?
... current_sign_in_at: datetime, last_sign_in_at: datetime,
current_sign_in_ip: string, last_sign_in_ip: string, created_at: datetime,
updated_at: datetime)"
Alternatively, having run rake db:create and rake db:migrate for your development environment, the file db/schema.rb will contain the author...
How does database indexing work? [closed]
...arising from the file systems size limits, careful thought must be used to select the correct fields to index.
Since indices are only used to speed up the searching for a matching field within the records, it stands to reason that indexing fields used only for output would be simply a waste of disk...
how to customize `show processlist` in mysql?
...
Newer versions of SQL support the process list in information_schema:
SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST
You can ORDER BY in any way you like.
The INFORMATION_SCHEMA.PROCESSLIST table was added in MySQL 5.1.7. You can find out which version you're using with:
SELECT VERSION()
...
How can I delete the current line in Emacs?
...lest way to delete (kill) a full line, from any point
on the line, without selecting anything, is:
C-w ; kill-region
It is versatile in deleting whatever is selected, or a line by default
if nothing is selected.
Given the question, you're probably also interested in replicating
Vim's "yank", yy...
How to use NULL or empty string in SQL
...
Select *
From Table
Where (col is null or col = '')
Or
Select *
From Table
Where IsNull(col, '') = ''
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improve t...
SQL Server indexes - ascending or descending, what difference does it make?
...TE INDEX ix_index ON mytable (col1, col2 DESC);
can be used for either:
SELECT *
FROM mytable
ORDER BY
col1, col2 DESC
or:
SELECT *
FROM mytable
ORDER BY
col1 DESC, col2
, but not for:
SELECT *
FROM mytable
ORDER BY
col1, col2
An index on a single colum...
How to move the cursor word by word in the OS X Terminal
...e sequences for you:
Open Terminal preferences (cmd+,);
At Settings tab, select Keyboard and double-click ⌥ ← if it's there, or add it if it's not.
Set the modifier as desired, and type the shortcut key in the box: esc+B, generating the text \033b (you can't type this text manually).
Repeat fo...