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MQTT接入EasyIoT平台 - 创客硬件开发 - 清泛IT社区，为创新赋能！
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代码差别主要在：地址、端口不同，且使用用户名、密码认证（这里仅仅是演示，隐藏了部分，以实际为准），订阅主题使用上面新建的。
本地SQLite实现注册登录功能 - App Inventor 2 中文网 - 清泛IT社区，为创新赋能！
建表的SQL语句如下：
CREATE TABLE user(username TEXT PRIMARY KEY, password TEXT);
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最后提一下日志调试功能：
上面其实是用户密码信息，在日志控制台中能够输出便于调试查看。
Simple way to calculate median with MySQL
...the simplest (and hopefully not too slow) way to calculate the median with MySQL? I've used AVG(x) for finding the mean, but I'm having a hard time finding a simple way of calculating the median. For now, I'm returning all the rows to PHP, doing a sort, and then picking the middle row, but surely ...
VIP会员中心 · App Inventor 2 中文网，少儿编程陪伴者
... 我家孩子在App Inventor 2 中文网的少儿编程课程中学到了如何设计自己的App，现在他已经可以独立开发一些简单的小应用了。很高兴看到他对于编程的兴趣和自信的提升！ ...
How to avoid mysql 'Deadlock found when trying to get lock; try restarting transaction'
...AL 900 SECOND
ORDER BY id
) u;
Another thing to keep in mind is that mysql documentation suggest that in case of a deadlock the client should retry automatically. you can add this logic to your client code. (Say, 3 retries on this particular error before giving up).
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Retrieving the last record in each group - MySQL
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MySQL 8.0 now supports windowing functions, like almost all popular SQL implementations. With this standard syntax, we can write greatest-n-per-group queries:
WITH ranked_messages AS (
SELECT m.*, ROW_NUMBER() OVER (PARTIT...
#1071 - Specified key was too long; max key length is 1000 bytes
...The INT(1) and INT(32) data types indicates another misunderstanding about MySQL. The numeric argument has no effect related to storage or the range of values allowed for the column. INT is always 4 bytes, and it always allows values from -2147483648 to 2147483647. The numeric argument is about p...
Show MySQL host via SQL Command
...last comment,
I don't think you can resolve IP for the hostname using pure mysql function,
as it require a network lookup, which could be taking long time.
However, mysql document mention this :-
resolveip google.com.sg
docs :- http://dev.mysql.com/doc/refman/5.0/en/resolveip.html
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MYSQL Truncated incorrect DOUBLE value
...ally whenever there is some Syntax issue it throws this useless exception "mysql-truncated-incorrect-double-value"
– heman123
May 10 '18 at 11:47
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MySQL - UPDATE query based on SELECT Query
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You can actually do this one of two ways:
MySQL update join syntax:
UPDATE tableA a
INNER JOIN tableB b ON a.name_a = b.name_b
SET validation_check = if(start_dts > end_dts, 'VALID', '')
-- where clause can go here
ANSI SQL syntax:
UPDATE tableA SET validation...