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Get records with max value for each group of grouped SQL results
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There's a super-simple way to do this in mysql:
select *
from (select * from mytable order by `Group`, age desc, Person) x
group by `Group`
This works because in mysql you're allowed to not aggregate non-group-by columns, in which case mysql just returns the first...
如何获取IE (控件)的所有链接（包括Frameset, iframe） - 其他 - 清泛IT社...
来源：新浪博客
IE 顶层 body 节点通过IHTMLElement->get_all 方法无法获取iframe 里面的节点列表：
CComPtr<IHTMLElement> body;
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CComPtr<IDispatch> spDispCollection;
body->get_all(&spDispCollection);复制代码所以要获取iframe/frame(frameset) ...
How to add new column to MYSQL table?
I am trying to add a new column to my MYSQL table using PHP. I am unsure how to alter my table so that the new column is created. In my assessment table I have:
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How do I update if exists, insert if not (AKA “upsert” or “merge”) in MySQL?
...SERT a row when it does not exist, or to UPDATE if it exists, using one MySQL query?
2 Answers
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Query to count the number of tables I have in MySQL
...long wait time. In that case, login should be done with the option -A, ie: mysql -uroot -p -A, and the command will work fast.
– azurecorn
Jul 21 at 12:28
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How to get UTF-8 working in Java webapps?
...s" those characters.
To get UTF-8 working under Java+Tomcat+Linux/Windows+Mysql requires the following:
Configuring Tomcat's server.xml
It's necessary to configure that the connector uses UTF-8 to encode url (GET request) parameters:
<Connector port="8080" maxHttpHeaderSize="8192"
maxThreads...
What does {0} mean when initializing an object?
..., a null pointer for pointers).
For non-scalar types (structures, arrays, unions), {0} specifies that the first element of the object is initialized to zero. For structures containing structures, arrays of structures, and so on, this is applied recursively, so the first scalar element is set to the...
MySQL: @variable vs. variable. What's the difference?
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MySQL has a concept of user-defined variables.
They are loosely typed variables that may be initialized somewhere in a session and keep their value until the session ends.
They are prepended with an @ sign, like this: @var
Yo...
Commands out of sync; you can't run this command now
I am trying to execute my PHP code, which calls two MySQL queries via mysqli, and get the error "Commands out of sync; you can't run this command now".
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What's the difference between utf8_general_ci and utf8_unicode_ci?
...ncoding. The differences are in how text is sorted and compared.
Note: In MySQL you have to use utf8mb4 rather than utf8. Confusingly, utf8 is a flawed UTF-8 implementation from early MySQL versions which remains only for backward compatibility. The fixed version was given the name utf8mb4.
Note: N...