大约有 40,000 项符合查询结果（耗时：0.0295秒） [XML]
How do I use regex in a SQLite query?
...ite manager. You need to invoke it slightly differently though, like this: SELECT * FROM table WHERE column regexp("myregexp")
– Tristan
May 30 '14 at 17:16
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2015年硅谷最火的高科技创业公司都有哪些 - 资讯 - 清泛网 - 专注C/C++及内核技术
...算机届最高奖以他命名)艰难的一生，他当年为破译德军密码制作了图灵机为二战胜利作出卓越贡献，挽回几千万人的生命，可在那个时代因为同性恋被判化学阉割，自杀结束了短暂的42岁生命。他的一个伟大贡献就是在人工智能...
ORA-00979 not a group by expression
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You must put all columns of the SELECT in the GROUP BY or use functions on them which compress the results to a single value (like MIN, MAX or SUM).
A simple example to understand why this happens: Imagine you have a database like this:
FOO BAR
0 A
0 ...
内存优化总结:ptmalloc、tcmalloc和jemalloc - 操作系统(内核) - 清泛网 - ...
... 总共32个vcpu。 16个table，每个5M row。
OLTP_RO测试包含5个select查询：select_ranges, select_order_ranges, select_distinct_ranges, select_sum_ranges,
可以看到在多核心或者多线程的场景下， jemalloc和tcmalloc带来的tps增加非常明显。
参考资料
glibc...
Importance of varchar length in MySQL table
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Anytime your select query uses a temporary table (group and order by operations, among other things) it will convert varchar(200) to a char(200) and performance will suffer.
– Jamie
Feb 7 '13 at 20:1...
Getting the difference between two sets
...ork but I think it would be a nice feature to have the set operations like union , difference built in java. The above solution will modify the set , in many situations we don't really want that.
– Praveen Kumar
Jul 18 '14 at 8:09
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How to send an email with Python?
...se user:
If you use 126/163, 网易邮箱, you need to set"客户端授权密码", like below:
ref: https://stackoverflow.com/a/41470149/2803344
https://docs.python.org/3/library/email.examples.html#email-examples
share
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How can I append a string to an existing field in MySQL?
... Alternatively you can use CONCAT_WS which skips NULL values. For example SELECT CONCAT_WS(', ','First name',NULL,'Last Name'); gives 'First name, Last Name'
– BarneySchmale
Aug 8 '16 at 11:00
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How to remove all namespaces from XML with C#?
... return new XElement(xmlDocument.Name.LocalName, xmlDocument.Elements().Select(el => RemoveAllNamespaces(el)));
}
It's working 100%, but I have not tested it much so it may not cover some special cases... But it is good base to start.
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How to request a random row in SQL?
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See this post: SQL to Select a random row from a database table. It goes through methods for doing this in MySQL, PostgreSQL, Microsoft SQL Server, IBM DB2 and Oracle (the following is copied from that link):
Select a random row with MySQL:
SELE...