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任何组件块 · App Inventor 2 中文网
... 参数为 true 组件。
考虑以下事件处理伪代码，看看它是如何工作的：
发生一个事件，例如用户单击名为 Button1 的按钮。
组件被初始化为Button1。
notAlreadyHandled 初始化为true。
App Inventor 检查 when Button1.Click 是否存在。
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How to convert timestamp to datetime in MySQL?
How to convert 1300464000 to 2011-03-18 16:00:00 in MySQL?
5 Answers
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Illegal mix of collations MySQL Error
...E your_table_name CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;
MySQL sneaks swedish in there sometimes for no sensible reason.
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Two single-column indexes vs one two-column index in MySQL?
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"MySQL can use multiple-column indexes for queries that test all the columns in the index, or queries that test just the first column, the first two columns, the first three columns, and so on. If you specify the columns in th...
What is the maximum value for an int32?
...e who accidentally stored the phone number as an INT instead of VARCHAR in MySQL.
– Zarel
Feb 9 '11 at 2:00
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MyISAM versus InnoDB [closed]
...o
But, frequent reading, almost no writing, use MyISAM
Full-text search in MySQL <= 5.5, use MyISAM
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MySQL Delete all rows from table and reset ID to zero
...wiping out. Enabling the foreign key checks after the fact does not cause MySQL to revalidate those foreign keys as far as I am aware. This leaves you with rows that contain data that does not exist in the reference table. You may as well not even have foreign keys on your table at all.
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How to use mysql JOIN without ON condition?
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MySQL documentation covers this topic.
Here is a synopsis. When using join or inner join, the on condition is optional. This is different from the ANSI standard and different from almost any other database. The effect is ...
Count with IF condition in MySQL query
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Or even SUM(ccc_news_comments.id = 'approved') as a MySQL-specific trick
– mojuba
Jan 21 '13 at 20:44
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MySQL Error 1215: Cannot add foreign key constraint
...the 4th point was my problem. It's kind of nasty - but I'm very very happy mysql did crash for that
– Sebas
Jun 16 '16 at 15:21
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