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Best way to select random rows PostgreSQL
...ery:
SELECT count(*) AS ct -- optional
, min(id) AS min_id
, max(id) AS max_id
, max(id) - min(id) AS id_span
FROM big;
The only possibly expensive part is the count(*) (for huge tables). Given above specifications, you don't need it. An estimate will do just fine,...
CSV API for Java [closed]
...nipulation of CSV cells. From http://super-csv.github.io/super-csv/examples_reading.html you'll find e.g.
given a class
public class UserBean {
String username, password, street, town;
int zip;
public String getPassword() { return password; }
public String getStreet() { return st...
What does |= (ior) do in Python?
...s1 |= s2 # 2
>>> s1.__ior__(s2) # 3
where the final value of s1 is equivalent either by:
an assigned OR operation
an in-place OR operation
an in-place OR operation via special method++
Example
Here we a...
联网 App 第 4 课：图片上传，压缩后用 Web 客户端传到服务器、列表直接显...
...设置的属性
图像选择器
图像选择器_选图
文本：从相册选图
图像
图像_预览
高度 220，勾选「自动缩放图片」
文本输入框
文本输入框_说明
按钮
...
Suppressing deprecated warnings in Xcode
...ry -Wno-deprecated-declarations, or its corresponding setting in Xcode, GCC_WARN_ABOUT_DEPRECATED_FUNCTIONS (pro tip: just type in "deprecated" in the build settings to find the specific setting for this warning).
Current versions of Xcode (e.g. Xcode 9.2):
Ancient versions of Xcode (e.g. Xcod...
Missing include “bits/c++config.h” when cross compiling 64 bit program on 32 bit in Ubuntu
...
While compiling in RHEL 6.2 (x86_64), I installed both 32bit and 64bit libstdc++-dev packages, but I had the "c++config.h no such file or directory" problem.
Resolution:
The directory /usr/include/c++/4.4.6/x86_64-redhat-linux was missing.
I did the foll...
How can I get current location from user in iOS
...be kept calling. Happy Coding Guys!! Cheers!!
– Apple_iOS0304
Mar 13 '13 at 4:07
5
You are the ty...
Check if URL has certain string with PHP
...URL and the rest check if it contains the word "car".
$url = 'http://' . $_SERVER['SERVER_NAME'] . $_SERVER['REQUEST_URI'];
if (strpos($url,'car') !== false) {
echo 'Car exists.';
} else {
echo 'No cars.';
}
shar...
How can I quantify difference between two images?
...ead images as 2D arrays (convert to grayscale for simplicity)
img1 = to_grayscale(imread(file1).astype(float))
img2 = to_grayscale(imread(file2).astype(float))
# compare
n_m, n_0 = compare_images(img1, img2)
print "Manhattan norm:", n_m, "/ per pixel:", n_m/img1.size
print "Z...
How do you format an unsigned long long int using printf?
...want to try using the inttypes.h library that gives you types such as
int32_t, int64_t, uint64_t etc.
You can then use its macros such as:
uint64_t x;
uint32_t y;
printf("x: %"PRId64", y: %"PRId32"\n", x, y);
This is "guaranteed" to not give you the same trouble as long, unsigned long long etc, ...