大约有 42,000 项符合查询结果（耗时：0.0400秒） [XML]
Insert into … values ( SELECT … FROM … )
... struggle to remember the correct syntax for the SQL engine of the day ( MySQL , Oracle , SQL Server , Informix , and DB2 ).
...
What does “coalgebra” mean in the context of programming?
...through all elements of A and b goes through all elements of B).
Disjoint union of two sets A and B is a set A | B which is a union of sets {(a, 1) : a in A} and {(b, 2) : b in B}. Essentially it is a set of all elements from both A and B, but with each of this elements 'marked' as belonging to eit...
How to add List to a List in asp.net [duplicate]
...
Use Concat or Union extension methods. You have to make sure that you have this direction using System.Linq; in order to use LINQ extensions methods.
Use the AddRange method.
...
“where 1=1” statement [duplicate]
I saw some people use a statement to query a table in a MySQL database like the following:
10 Answers
...
Boost.Asio的简单使用(Timer,Thread,Io_service类) - C/C++ - 清泛网 - 专注C/C++及内核技术
...io的简单使用(Timer,Thread,Io_service类)2. 同步Timer本章介绍asio如何在定时器上进行阻塞等待(blocking wait).实现,我们包含必要的头文件.所有的asio类可以简单的通过include "...目录：
1. 同步Timer
2. 异步Timer
3. 回调函数的参数
4. 成员函...
Difference between string and text in rails?
...l is converted into its respective column type in query language.
with MySQL :string is mapped to VARCHAR(255)
- http://guides.rubyonrails.org/migrations.html
:string | VARCHAR | :limit => 1 to 255 (default = 255)
:text | TINYTEXT, TEXT, MEDIUMTEXT, or...
Delete terminal history in Linux [closed]
...can use previous commands again. Great feature. However, I started logging mysql into mysql with the sensitive details in the command.
...
JOIN queries vs multiple queries
... you are joining 3 or more tables on different keys, often databases (i.e. mysql) can only use one index per table, meaning maybe one of the joins will be fast (and use an index) whereas the others will be extremely slow. For multiple queries, you can optimize the indexes to use for each query.
...
On duplicate key ignore? [duplicate]
...because it will additionally hold Next-Key lock on your indexes. More: dev.mysql.com/doc/refman/5.7/en/…
– Dzmitry Lazerka
Mar 14 '17 at 7:13
1
...
Error Code: 1005. Can't create table '…' (errno: 150)
...exceeds the maximum length of 64 characters.
For more details, refer to: MySQL Error Number 1005 Can’t create table
share
|
improve this answer
|
follow
|
...