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mysql实现split分割字符串（length, SUBSTRING_INDEX, substring） - 爬虫/...
由于MySql没有直接的split函数，只提供了length, SUBSTRING_INDEX, substring三个函数，这里介绍如何用这三个函数实现split功能。
# SUBSTRING_INDEX(str, delim, count)：返回字符串 str 中在第 count 个出现的分隔符 delim 之前的子串。如果 count 是...
Mysql substr和Oracle substr区别 - 爬虫/数据库 - 清泛IT社区，为创新赋能！
Oracle substr(字符串，开始索引、从0起，长度)
Mysql substr或substring(字符串，开始索引、从1起，长度)
Why is a “GRANT USAGE” created the first time I grant a user privileges?
...to the admin side of DBMS and was setting up a new database tonight (using MySQL) when I noticed this. After granting a user a privilege for the first time, another grant is created that looks like
...
Parsing XML with namespace in Python via 'ElementTree'
...mespaces = {'owl': 'http://www.w3.org/2002/07/owl#'} # add more as needed
root.findall('owl:Class', namespaces)
Prefixes are only looked up in the namespaces parameter you pass in. This means you can use any namespace prefix you like; the API splits off the owl: part, looks up the corresponding n...
cpuid汇编指令 - C/C++ - 清泛网 - 专注C/C++及内核技术
...一组返回的是基本信息，另一组返回的是扩展信息。
1、如何判断CPU是否支持CPUID指令
前面说过，大概是从80486开始才有的cpuid这个指令，是不是所有的80486家族CPU都有这个指令我也不是很清楚，但在EFLAGS中的bit 21可以识别CPU...
How to change the default GCC compiler in Ubuntu?
...
@thang also called cc: root@host:/root# update-alternatives --get-selections | grep '/usr/bin/gcc' cc auto /usr/bin/gcc
– jopasserat
Aug 13 '16 at 15:26
...
How do I find a “gap” in running counter with SQL?
...
In MySQL and PostgreSQL:
SELECT id + 1
FROM mytable mo
WHERE NOT EXISTS
(
SELECT NULL
FROM mytable mi
WHERE mi.id = mo.id + 1
)
ORDER BY
id
LIMIT 1
In SQL Server:
...
What is the difference between 127.0.0.1 and localhost
...
@DonViegues That's MySQL specific and IMO bad design. It will see localhost and tries to use unix-socket instead of connecting using IP but for 127.0.0.1 it just uses IP.
– Arman Ordookhani
Jul 18 '19 at 8...
Mysql error 1452 - Cannot add or update a child row: a foreign key constraint fails
...s another, but it is failing for some reason. With my limited knowledge of MySQL, the only thing that could possibly be suspect is that there is a foreign key on a different table referencing the one I am trying to reference.
...
MySQL: How to copy rows, but change a few fields?
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MySQL supports the TEMPORARY keyword to create temporary tables. Usage of CREATE TEMPORARY TABLE will automagically drop the table when the session (a serie of SQL queries) is finished. Dropping the table wouldn't be necessar...