大约有 30,000 项符合查询结果（耗时：0.0514秒） [XML]
How to group time by hour or by 10 minutes
...ind of guy)
In Oracle:
SELECT timeslot, COUNT(*)
FROM
(
SELECT to_char(l_time, 'YYYY-MM-DD hh24') timeslot
FROM
(
SELECT l_time FROM mytab
)
) GROUP BY timeslot
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How to vertically align an image inside a div
...ng" height=3px />
</div>
Or, if you don't want to have an extra element in modern browsers and don't mind using Internet Explorer expressions, you can use a pseudo-element and add it to Internet Explorer using a convenient Expression, that runs only once per element, so there won't ...
Comment out text in R Markdown (Rmd file)
...
Extra yaml blocks can be used anywhere inside the document, and commented out with #
---
title: "Untitled"
output: html_document
---
No comment.
---
# here's a comment
# ```{r}
# x = pi
# ```
---
Note however that this ...
Which timestamp type should I choose in a PostgreSQL database?
... (
my_timestamp TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW(),
CHECK(EXTRACT(TIMEZONE FROM my_timestamp) = '0')
);
test=> SET timezone = 'America/Los_Angeles';
SET
test=> INSERT INTO my_tbl (my_timestamp) VALUES (NOW());
ERROR: new row for relation "my_tbl" violates check constraint "my...
Number of rows affected by an UPDATE in PL/SQL
...m a plain command, the solution could be:
begin
DBMS_OUTPUT.PUT_LINE(TO_Char(SQL%ROWCOUNT)||' rows affected.');
end;
The basic problem is that SQL%ROWCOUNT is a PL/SQL variable (or function), and cannot be directly accessed from an SQL command. By using a noname PL/SQL block, this can be achiev...
Best way to store password in database [closed]
...note that a common misconception is to simply add the same unique and long string to all passwords; while this is not horrible, it is best to add unique salts to every password. Read this for more.
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How to express a One-To-Many relationship in Django
...ionship on the PhoneNumber model and not on the Dude/Business models. When extra terrestrials come to Earth, and we want to add an Alien model, we need to modify the PhoneNumber (assuming the ETs have phone numbers) instead of simply adding a "phone_numbers" field to the Alien model.
Introduce the...
Checking for NULL pointer in C/C++ [closed]
...ad and more explicit. I see where they're coming from, I just disagree the extra stuff makes it any easier. (I hate the macro, so I'm biased.) Up to you.
I disagree with your argument. If you're not getting warnings for assignments in a conditional, you need to turn your warning levels up. Simple a...
Five equal columns in twitter bootstrap
...
Update 2019
Bootstrap 4.1+
Here are 5 equal, full-width columns (no extra CSS or SASS) using the auto-layout grid:
<div class="container-fluid">
<div class="row">
<div class="col">1</div>
<div class="col">2</div>
<div class="...
How to “log in” to a website using Python's Requests module?
...e script when trying to log into sites with unverified SSL certificates.
Extra:
To run this script from the command line on a UNIX based system place it in a directory, i.e. home/scripts and add this directory to your path in ~/.bash_profile or a similar file used by the terminal.
# Custom scrip...