大约有 40,000 项符合查询结果（耗时：0.0638秒） [XML]
How to concatenate strings of a string field in a PostgreSQL 'group by' query?
...at the question asked for, even letting you specify the delimiter string:
SELECT company_id, string_agg(employee, ', ')
FROM mytable
GROUP BY company_id;
Postgres 9.0 also added the ability to specify an ORDER BY clause in any aggregate expression; otherwise, the order is undefined. So you can no...
How to use UIScrollView in Storyboard
...
Here are the steps with Auto Layout that worked for me on XCode 8.2.1.
Select Size Inspector of View Controller, and change Simulated Size to Freeform with height 1000 instead of Fixed.
Rename the view of View Controller as RootView.
Drag a Scroll View as subview of RootView and rename it as Scr...
How to split a String by space
...the trim caveat, you might want to consider the unicode non-breaking space character (U+00A0). This character prints just like a regular space in string, and often lurks in copy-pasted text from rich text editors or web pages. They are not handled by .trim() which tests for characters to remove usin...
How can I use if/else in a dictionary comprehension?
...ry for further processing like validation, or editing which we must return selected data from file back to entry widgets, etc.
The first round using traditional coding (8 lines):
entries = {'name': 'Material Name', 'maxt': 'Max Working Temperature', 'ther': {100: 1.1, 200: 1.2}}
a_dic, b_dic = {}, ...
JSON.NET Error Self referencing loop detected for type
...ceLoopHandling = ReferenceLoopHandling.Ignore,
}, ArrayPool<char>.Shared));
});
}
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django: BooleanField, how to set the default value to true?
...ou want to dynamically choose at runtime whether or not your field will be selected by default, you can use the initial parameter to the form when you initialize it:
form = MyForm(initial={'my_field':True})
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Fast ceiling of an integer division in C / C++
... return res.rem ? (res.quot + 1) : res.quot;
}
int main(int, const char**)
{
std::cout << "10 / 5 = " << div_ceil(10, 5) << std::endl;
std::cout << "11 / 5 = " << div_ceil(11, 5) << std::endl;
return 0;
}
...
MySQL复制的概述、安装、故障、技巧、工具 - 数据库(内核) - 清泛网 - 专注...
...表可以使用不同的键类型。比如主服务器用InnoDB，键用VARCHAR的话节省空间，从服务器使用MyISAM，键用CHAR提高速度，因为MyISAM有静态表一说。
主从服务器中的表可以使用不同的索引。主服务器主要用来应付写操作，所以除了主...
Get table names using SELECT statement in MySQL
...
To get the name of all tables use:
SELECT table_name FROM information_schema.tables;
To get the name of the tables from a specific database use:
SELECT table_name FROM information_schema.tables
WHERE table_schema = 'your_database_name';
Now, to answer the...
How to get object size in memory? [duplicate]
...would know, Int32 and float are four
bytes, double and DateTime 8 bytes, char is actually two bytes (not
one byte), and so on. String is a bit more complex, 2*(n+1), where n
is the length of the string. For objects, it will depend on their
members: just sum up the memory requirement of all i...