大约有 43,000 项符合查询结果（耗时：0.0446秒） [XML]
Reshaping data.frame from wide to long format
...
Here is another example showing the use of gather from tidyr. You can select the columns to gather either by removing them individually (as I do here), or by including the years you want explicitly.
Note that, to handle the commas (and X's added if check.names = FALSE is not set), I am also us...
Acronyms in CamelCase [closed]
...n using acronyms, use Pascal case or camel case for acronyms more than two characters long. For example, use HtmlButton or htmlButton. However, you should capitalize acronyms that consist of only two characters, such as System.IO instead of System.Io.
Do not use abbreviations in identifiers or ...
Postgres DB Size Command
..."pg_datbase" system table. Just apply the function to the names, as below.
select t1.datname AS db_name,
pg_size_pretty(pg_database_size(t1.datname)) as db_size
from pg_database t1
order by pg_database_size(t1.datname) desc;
If you intend the output to be consumed by a machine instead of a...
Ruby Arrays: select(), collect(), and map()
...re, to check the :qty key, you'd do something like the following:
details.select{ |item| item[:qty] != "" }
That will give you all items where the :qty key isn't an empty string.
official select documentation
share
...
Dump a mysql database to a plaintext (CSV) backup from the command line
... separated) files which can import into Excel, etc, quite easily:
% echo 'SELECT * FROM table' | mysql -B -uxxx -pyyy database
Alternatively, if you've got direct access to the server's file system, use SELECT INTO OUTFILE which can generate real CSV files:
SELECT * INTO OUTFILE 'table.csv'
...
Disable dragging an image from an HTML page
...
But this lead to the weird selection effect in FF atleast. Better still return false;
– Bhumi Singhal
Feb 22 '13 at 10:24
...
How do I select the “last child” with a specific class name in CSS? [duplicate]
How do I select the "last child" with the class name: list ?
6 Answers
6
...
CSS Selector that applies to elements with two classes
Is there a way to select an element with CSS based on the value of the class attribute being set to two specific classes. For example, let's say I have 3 divs:
...
Finding duplicate values in MySQL
...
Do a SELECT with a GROUP BY clause. Let's say name is the column you want to find duplicates in:
SELECT name, COUNT(*) c FROM table GROUP BY name HAVING c > 1;
This will return a result with the name value in the first colum...
MongoDB relationships: embed or reference?
...ill tied to text messages and Ruby 1.4 strings; in other words still ASCII chars only.
– John F. Miller
Sep 8 '17 at 18:52
|
show 4 more com...