大约有 43,000 项符合查询结果（耗时：0.0125秒） [XML]
How to reshape data from long to wide format
...mes(df) <- unique(dat1$name)
df
sqldf package:
library(sqldf)
sqldf('SELECT name,
MAX(CASE WHEN numbers = 1 THEN value ELSE NULL END) x1,
MAX(CASE WHEN numbers = 2 THEN value ELSE NULL END) x2,
MAX(CASE WHEN numbers = 3 THEN value ELSE NULL END) x3,
MAX(CASE WHEN numbe...
How do we count rows using older versions of Hibernate (~2009)?
...eturn int and use this form:
int count = ((Long)getSession().createQuery("select count(*) from Book").uniqueResult()).intValue();
share
|
improve this answer
|
follow
...
How to randomly select rows in SQL?
...
SELECT TOP 5 Id, Name FROM customerNames
ORDER BY NEWID()
That said, everybody seems to come to this page for the more general answer to your question:
Selecting a random row in SQL
Select a random row with MySQL:
SELECT...
SQL query for today's date minus two months
I want to select all the records in a table where their date of entry is older then 2 months.
5 Answers
...
How to get the first and last date of the current year?
...
SELECT
DATEADD(yy, DATEDIFF(yy, 0, GETDATE()), 0) AS StartOfYear,
DATEADD(yy, DATEDIFF(yy, 0, GETDATE()) + 1, -1) AS EndOfYear
The above query gives a datetime value for midnight at the beginning of December 31. This ...
How do you convert a DataTable into a generic list?
...ataTable
//using lamdaexpression
emp = (from DataRow row in dt.Rows
select new Employee
{
_FirstName = row["FirstName"].ToString(),
_LastName = row["Last_Name"].ToString()
}).ToList();
share
...
Getting only Month and Year from SQL DATE
...o 'discard' the Days, Hours, etc
- Leaving a year/month only date field
SELECT
DATEADD(MONTH, DATEDIFF(MONTH, 0, <dateField>), 0) AS [year_month_date_field]
FROM
<your_table>
This gets the number of whole months from a base date (0) and then adds them to that base date. Thus ...
Cast List to List
... clientList = new List<Client>();
List<IDic> list = clientList.Select(c => (IDic)c).ToList();
share
|
improve this answer
|
follow
|
...
Compare two objects' properties to find differences?
...pe t1, Type t2) {
var list1 = t1.GetProperties().OrderBy(x => x.Name).Select(x => x.Name);
var list2 = t2.GetProperties().OrderBy(x => x.Name).Select(x => x.Name);
return list1.SequenceEqual(list2);
}
shar...
How enumerate all classes with custom class attribute?
... faster (especially without empirical proof); you've basically written the Select extension method, and the compiler will generate a state machine just as it would if you called Select because of your use of yield return. Finally, any performance gains that might be obtained in the majority of case...