大约有 47,000 项符合查询结果（耗时：0.0345秒） [XML]
Only read selected columns
...from the data.table-package:
You can specify the desired columns with the select parameter from fread from the data.table package. You can specify the columns with a vector of column names or column numbers.
For the example dataset:
library(data.table)
dat <- fread("data.txt", select = c("Year...
Count work days between two dates
...
For workdays, Monday to Friday, you can do it with a single SELECT, like this:
DECLARE @StartDate DATETIME
DECLARE @EndDate DATETIME
SET @StartDate = '2008/10/01'
SET @EndDate = '2008/10/31'
SELECT
(DATEDIFF(dd, @StartDate, @EndDate) + 1)
-(DATEDIFF(wk, @StartDate, @EndDate) *...
python list in sql query as parameter
...I paramstyle.
placeholders= ', '.join(placeholder for unused in l)
query= 'SELECT name FROM students WHERE id IN (%s)' % placeholders
cursor.execute(query, l)
share
|
improve this answer
|...
INSERT INTO … SELECT FROM … ON DUPLICATE KEY UPDATE
...olumns named in the INSERT INTO clause, and the second part references the SELECT columns.
INSERT INTO lee(exp_id, created_by, location, animal, starttime, endtime, entct,
inact, inadur, inadist,
smlct, smldur, smldist,
larct, lardur, lardist,
...
How to “add existing frameworks” in Xcode 4?
...
As per Apple's documentation:
In the project navigator, select
your project.
Select your target.
Select the "Build Phases" tab.
Open "Link Binaries With Libraries"
expander.
Click the + button.
Select your framework.
(optional) Drag and drop the added
framework to the "Framework...
Difference Between Select and SelectMany
I've been searching the difference between Select and SelectMany but I haven't been able to find a suitable answer. I need to learn the difference when using LINQ To SQL but all I've found are standard array examples.
...
How to add MVC5 to Visual Studio 2013?
...onger has separate project types for different ASP.Net features.
You must select .NET Framework 4.5 (or higher) in order to see the ASP.NET Web Application template (For ASP.NET One).
So just select Visual C# > Web > ASP.NET Web Application, then select the MVC checkbox in the next step.
Not...
Select last N rows from MySQL
I want to select last 50 rows from MySQL database within column named id which is primary key . Goal is that the rows should be sorted by id in ASC order, that’s why this query isn’t working
...
Left Join With Where Clause
...ring away rows where the left join doesn't succeed. Move it to the join:
SELECT `settings`.*, `character_settings`.`value`
FROM `settings`
LEFT JOIN
`character_settings`
ON `character_settings`.`setting_id` = `settings`.`id`
AND `character_settings`.`character_id` = '1'
...
How to concatenate strings of a string field in a PostgreSQL 'group by' query?
...at the question asked for, even letting you specify the delimiter string:
SELECT company_id, string_agg(employee, ', ')
FROM mytable
GROUP BY company_id;
Postgres 9.0 also added the ability to specify an ORDER BY clause in any aggregate expression; otherwise, the order is undefined. So you can no...