大约有 48,000 项符合查询结果（耗时：0.0446秒） [XML]
Remove an entire column from a data.frame in R
...=4:6)
to remove just the a column you could do
Data <- subset( Data, select = -a )
and to remove the b and d columns you could do
Data <- subset( Data, select = -c(d, b ) )
You can remove all columns between d and b with:
Data <- subset( Data, select = -c( d : b )
As I said above...
What is the difference between HAVING and WHERE in SQL?
What is the difference between HAVING and WHERE in an SQL SELECT statement?
20 Answers
...
Select all columns except one in MySQL?
I'm trying to use a select statement to get all of the columns from a certain MySQL table except one. Is there a simple way to do this?
...
Is there a function to deselect all text using JavaScript?
Is there a function in javascript to just deselect all selected text? I figure it's got to be a simple global function like document.body.deselectAll(); or something.
...
C: Run a System Command and Get Output? [duplicate]
I want to run a command in linux and get the text returned of what it outputs, but I do not want this text printed to screen. Is there a more elegant way than making a temporary file?
...
How to create .ipa file using Xcode?
...
In Xcode Version 10.0
Go to Window -> Organizer
Then select your app archive from archives
Then click the "Distribute App" button on right panel
Then follow the below steps
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6 : Finally select the place you want to sa...
Using column alias in WHERE clause of MySQL query produces an error
... though, by putting the expression directly into the WHERE x IN y clause:
SELECT `users`.`first_name`,`users`.`last_name`,`users`.`email`,SUBSTRING(`locations`.`raw`,-6,4) AS `guaranteed_postcode`
FROM `users` LEFT OUTER JOIN `locations`
ON `users`.`id` = `locations`.`user_id`
WHERE SUBSTRING(`loca...
How to round an average to 2 decimal places in PostgreSQL?
... round that takes a precision is only available for numeric.
regress=> SELECT round( float8 '3.1415927', 2 );
ERROR: function round(double precision, integer) does not exist
regress=> \df *round*
List of functions
Schema | Name | Result data type | Argument...
How to set Sqlite3 to be case insensitive when string comparing?
I want to select records from sqlite3 database by string matching. But if I use '=' in the where clause, I found that sqlite3 is case sensitive. Can anyone tell me how to use string comparing case-insensitive?
...
Can someone explain collection_select to me in clear, simple terms?
I am going through the Rails API docs for collection_select and they are god-awful.
2 Answers
...