大约有 47,000 项符合查询结果（耗时：0.0461秒） [XML]
Return 0 if field is null in MySQL
...
Use IFNULL:
IFNULL(expr1, 0)
From the documentation:
If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.
...
On localhost, how do I pick a free port number?
...do I figure out which port is available? I assume I cannot listen on port 80 or 21?
5 Answers
...
JavaScript function to add X months to a date
...getMonth() + +months);
if (date.getDate() != d) {
date.setDate(0);
}
return date;
}
// Add 12 months to 29 Feb 2016 -> 28 Feb 2017
console.log(addMonths(new Date(2016,1,29),12).toString());
// Subtract 1 month from 1 Jan 2017 -> 1 Dec 2016
console.log(addMonths(n...
Why does this code using random strings print “hello world”?
...onstructed with a specific seed parameter (in this case -229985452 or -147909649), it follows the random number generation algorithm beginning with that seed value.
Every Random constructed with the same seed will generate the same pattern of numbers every time.
...
How to send a simple string between two programs using pipes?
... "/tmp/myfifo";
/* create the FIFO (named pipe) */
mkfifo(myfifo, 0666);
/* write "Hi" to the FIFO */
fd = open(myfifo, O_WRONLY);
write(fd, "Hi", sizeof("Hi"));
close(fd);
/* remove the FIFO */
unlink(myfifo);
return 0;
}
reader.c
#include <fcntl.h>
#i...
Regular expression for first and last name
...
202
Don't forget about names like:
Mathias d'Arras
Martin Luther King, Jr.
Hector Sausage-Hausen
...
What is a method that can be used to increment letters?
...
180
Simple, direct solution
function nextChar(c) {
return String.fromCharCode(c.charCodeAt(0) +...
Find the extension of a filename in Ruby
...
That's really basic stuff:
irb(main):002:0> accepted_formats = [".txt", ".pdf"]
=> [".txt", ".pdf"]
irb(main):003:0> File.extname("example.pdf") # get the extension
=> ".pdf"
irb(main):004:0> accepted_formats.include? File.extname("example.pdf")
=...
How to remove space between axis & area-plot in ggplot2?
... to expand the scale by 5% on each side for
continuous variables, and by 0.6 units on each side for discrete
variables.
The problem is thus solved by adding expand = c(0,0) to scale_x_continuous and scale_y_continuous. This also removes the need for adding the panel.margin parameter.
The code...
A simple explanation of Naive Bayes Classification
...les, would receive misleadingly high scores.
In general, for an example, 70% of our data can be used as training set cases. Also remember to partition the original set into the training and test sets randomly.
Now I come to your other question about Naive Bayes.
To demonstrate the concept of Naï...