大约有 44,000 项符合查询结果（耗时：0.0245秒） [XML]
varbinary to string on SQL Server
...AST it
declare @b varbinary(max)
set @b = 0x5468697320697320612074657374
select cast(@b as varchar(max)) /*Returns "This is a test"*/
This is the equivalent of using CONVERT with a style parameter of 0.
CONVERT(varchar(max), @b, 0)
Other style parameters are available with CONVERT for differ...
How to include “zero” / “0” results in COUNT aggregate?
...n outer join for this (and you need to use person as the "driving" table)
SELECT person.person_id, COUNT(appointment.person_id) AS "number_of_appointments"
FROM person
LEFT JOIN appointment ON person.person_id = appointment.person_id
GROUP BY person.person_id;
The reason why this is working, i...
How to select a radio button by default? [duplicate]
I have some radio buttons and I want one of them to be set as selected by default when the page is loaded. How can I do that?
...
How to get number of rows using SqlDataReader in C#
...reading all rows (and then you might as well store them)
run a specialized SELECT COUNT(*) query beforehand.
Going twice through the DataReader loop is really expensive, you would have to re-execute the query.
And (thanks to Pete OHanlon) the second option is only concurrency-safe when you use a ...
How can I find non-ASCII characters in MySQL?
...ng as "ASCII", but I would suggest trying a variant of a query like this:
SELECT * FROM tableName WHERE columnToCheck NOT REGEXP '[A-Za-z0-9]';
That query will return all rows where columnToCheck contains any non-alphanumeric characters. If you have other characters that are acceptable, add them ...
Could not find an implementation of the query pattern
...ed to do it using:
var query = (from p in tblPersoon.Cast<Person>() select p).Single();
This kind of error (Could not find an implementation of the query pattern) usually occurs when:
You are missing LINQ namespace usage (using System.Linq)
Type you are querying does not implement IEnumer...
Extracting specific columns from a data frame
...r package, if your data.frame is called df1:
library(dplyr)
df1 %>%
select(A, B, E)
This can also be written without the %>% pipe as:
select(df1, A, B, E)
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What is causing this ActiveRecord::ReadOnlyRecord error?
...s automatically inferred only if :joins was specified without an explicit :select nor an explicit (or finder-scope-inherited) :readonly option (see the implementation of set_readonly_option! in active_record/base.rb for Rails 2.3.4, or the implementation of to_a in active_record/relation.rb and of c...
How can I remove duplicate rows?
...
Assuming no nulls, you GROUP BY the unique columns, and SELECT the MIN (or MAX) RowId as the row to keep. Then, just delete everything that didn't have a row id:
DELETE FROM MyTable
LEFT OUTER JOIN (
SELECT MIN(RowId) as RowId, Col1, Col2, Col3
FROM MyTable
GROUP BY Co...
“Unresolved inclusion” error with Eclipse CDT for C standard library headers
...lipse, you open the Properties of your project, expand "C/C++ General" and select "Paths and Symbols".
Make sure you have added the include dir for each language you are using. (In my case, I needed to just add it to GNU C++.)
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