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Does MySQL ignore null values on unique constraints?
... '1' for key 'x'
INSERT table1 VALUES (NULL);
INSERT table1 VALUES (NULL);
SELECT * FROM table1;
Result:
x
NULL
NULL
1
This is not true for all databases. SQL Server 2005 and older, for example, only allows a single NULL value in a column that has a unique constraint.
...
LR性能测试结果样例分析 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...场景执行过程中SQL语句的执行情况，从图中可以看到，“Selects（查询）”与“Inserts（插入）”两种语句执行的趋势在场景执行过程中是比较平滑，并且测试中没有错误发现，也就说明在处理相关业务时Mysql的处理是正常的。假...
Does Swift have documentation generation support?
...
New in Xcode 8, you can select a method like this
func foo(bar: Int) -> String { ... }
Then press command + option + / or choose "Structure" - "Add documentation" from Xcode's "Editor" menu, and it will generate the following comments template...
ASP.NET Web Site or ASP.NET Web Application?
...e solution is very fast, and you can always click on the Web Site node and select Build, if you’ve made changes.
In an MVC Web Application project you have extra commands and dialogs for common tasks, like ‘Add View’, ‘Go To View’, ‘Add Controller’, etc. These are not available in an ...
Styling input buttons for iPad and iPhone
...
One issue with this is that for <select> boxes, it doesn't display the arrow when on a Desktop browser. So this is best paired with a media query I think.
– andrewtweber
Mar 19 '13 at 2:21
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What is the difference between the Data Mapper, Table Data Gateway (Gateway), Data Access Object (DA
...ata Gateway is used mainly for a single table or view. It contains all the selects, inserts, updates, and deletes. So Customer is a table or a view in your case. So, one instance of a table data gateway object handles all the rows in the table. Usually this is related to one object per database tabl...
Mapping composite keys using EF code first
...f(ColumnAttribute.Order))
.TypedValue.Value ?? 0)
.Select(x => x.Name)
.ToArray();
// apply the keys to the model builder
modelBuilder.Entity(entity.ClrType).HasKey(orderedKeys);
}
I haven't fully tested this in all situations, but it works in my basic t...
Dynamically change color to lighter or darker by percentage CSS (Javascript)
...
@imjared This must be selected as answer... Thanks.
– Jack
Dec 14 '18 at 10:54
...
Pointer to class data member “::*”
...unction that would do some pre &post processing before applying a user-selected member function to an object:
void Apply( SomeClass * c, void (SomeClass::*func)() ) {
// do hefty pre-call processing
(c->*func)(); // call user specified function
// do hefty post-call processing
}...
What is “stdafx.h” used for in Visual Studio?
...is setting is controlled from the GUI via Right-clicking on a CPP Project, selecting 'Properties' and navigating to "Configuration Properties\C/C++\Precompiled Headers". For other versions of Visual Studio, the location in the GUI will be different.
Note that if you disable precompiled headers (or ...