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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
...
Convert a Git folder to a submodule retrospectively?
...ven though I have tested this successfully)!
0. Preparation
Variables
# Root directory where repo-org lives
# and a temporary location for git filter-branch
root="$PWD"
temp='/dev/shm/tmp'
# The old repository and the subdirectory we'd like to extract
repo_old="$root/repo-old"
repo_old_directory...
JRE 1.7 - java version - returns: java/lang/NoClassDefFoundError: java/lang/Object
...-r -v rt.pack rt.jar
To recursively unpack all .pack files, from the JRE root run:
for /r %f in (*.pack) do "%JAVA_HOME%\bin\unpack200.exe" -r -q "%f" "%~pf%~nf.jar"
*nix
To unpack one .pack file (for example rt.pack), run:
/usr/bin/unpack200 -r -v rt.pack rt.jar
To recursively unpack all ....
新手程序员应该知道的7件事 - 创意 - 清泛网 - 专注C/C++及内核技术
...。掌握类似于find、comm、diff、vi/vim、sed、awk等工具。知道如何用命令行来查找文件等等，都可以在你写脚本的时候为你减负。”
Bull，是一位先用微软工具，然后逐渐转移到Linux的程序员，对此表示赞同：“了解命令行的来龙去...
iOS开发调试技巧总结 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...复杂。这样就给我们新接手项目的开发者带来很多困扰。如何快速查看一个复杂UI的界面层次和布局，最快的方法就是用到视图调试。
当项目运行到某一个界面（可以是模拟器或真机）时，开启视图调试，点击按钮如图：
这样...
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...
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:
...
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...
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.
...