大约有 49,000 项符合查询结果（耗时：0.0390秒） [XML]
When should I use a composite index?
...nefit a query that uses those fields for joining, filtering, and sometimes selecting. It will also benefit queries that use left-most subsets of columns in that composite. So the above index will also satisfy queries that need
index( column_A, column_B, column_C )
index( column_A, column_B )
index(...
How do I repeat an edit on multiple lines in Vim?
...al block by using
" allow the . to execute once for each line of a visual selection
vnoremap . :normal .<CR>
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Could not instantiate class named MKMapView
... project to bring the project settings. Under Targets, click your project, select from the upper toolbar "Build Phases". Under "Link binary With Libraries" tab, you will see the list of frameworks included in your project. Click the "+" button and add MapKit library from the shown list to your proje...
IN vs OR in the SQL WHERE Clause
...h are nearly instant. When the column is not indexed I got these results:
SELECT COUNT(*) FROM t_inner WHERE val IN (1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000);
1 row fetched in 0.0032 (1.2679 seconds)
SELECT COUNT(*) FROM t_inner WHERE val = 1000 OR val = 2000 OR val = 3000 OR val = 40...
How can I easily convert DataReader to List? [duplicate]
... writing an extension method for this:
public static IEnumerable<T> Select<T>(this IDataReader reader,
Func<IDataReader, T> projection)
{
while (reader.Read())
{
yield return projection(reader);
}
}
You can then use LINQ...
Import CSV file into SQL Server
...e using SQL Server Management Studio
• Right click on your database and select Tasks -> Import Data...
• Click the Next > button
• For the Data Source, select Flat File Source. Then use the Browse button to select the CSV file. Spend some time configuring how you want the data to be...
How to create a sequence of integers in C#?
...
Linq projection with the rarely used indexer overload (i):
(new int[11]).Select((o,i) => i)
I prefer this method for its flexibilty.
For example, if I want evens:
(new int[11]).Select((item,i) => i*2)
Or if I want 5 minute increments of an hour:
(new int[12]).Select((item,i) => i*5...
How to make ReSharper re-evaluate its assembly reference highlighting
... unload the project, right-click the project in the solution explorer, and select Unload Project. Then, right-click the project again and select Reload Project.
The issue continues to occur occasionally with the latest versions of ReSharper, but the fix seems to work for every version.
...
Manually map column names with class properties
...
This works fine:
var sql = @"select top 1 person_id PersonId, first_name FirstName, last_name LastName from Person";
using (var conn = ConnectionFactory.GetConnection())
{
var person = conn.Query<Person>(sql).ToList();
return person;
}
Da...
How to delete a workspace in Eclipse?
...Mac OS, once you have deleted the actual workspace directory the option to select and switch to that workspace will still be available unless you delete the entry from Preferences >> General >> Startup and Shutdown >> Workspaces.
...