大约有 45,000 项符合查询结果（耗时：0.0322秒） [XML]
In .NET, which loop runs faster, 'for' or 'foreach'?
...
Enumerable.Select has an overload that lets you obtain the index of the item, so even the need for an index does not mandate using for. See msdn.microsoft.com/en-us/library/bb534869.aspx
– TrueWill
...
How to count occurrences of a column value efficiently in SQL?
...
This should work:
SELECT age, count(age)
FROM Students
GROUP by age
If you need the id as well you could include the above as a sub query like so:
SELECT S.id, S.age, C.cnt
FROM Students S
INNER JOIN (SELECT age, count(age) a...
Android getting value from selected radiobutton
... @Override
public void onClick(View v) {
// get selected radio button from radioGroup
int selectedId = radioGroup.getCheckedRadioButtonId();
// find the radiobutton by returned id
radioButton = (RadioButton) findViewById(selectedId);
...
Postgres manually alter sequence
...
The parentheses are misplaced:
SELECT setval('payments_id_seq', 21, true); # next value will be 22
Otherwise you're calling setval with a single argument, while it requires two or three.
...
Only one expression can be specified in the select list when the subquery is not introduced with EXI
...column on the other side of the IN. So the query needs to be of the form:
SELECT * From ThisTable WHERE ThisColumn IN (SELECT ThatColumn FROM ThatTable)
You also want to add sorting so you can select just from the top rows, but you don't need to return the COUNT as a column in order to do your so...
MySQL order by before group by
... table on both the post_author and the max date.
The solution should be:
SELECT p1.*
FROM wp_posts p1
INNER JOIN
(
SELECT max(post_date) MaxPostDate, post_author
FROM wp_posts
WHERE post_status='publish'
AND post_type='post'
GROUP BY post_author
) p2
ON p1.post_author = p...
How do I check if a number is positive or negative in C#?
...
This is the industry standard:
int is_negative(float num)
{
char *p = (char*) malloc(20);
sprintf(p, "%f", num);
return p[0] == '-';
}
share
|
improve this answer
|
...
Which, if any, C++ compilers do tail-recursion optimization?
...t for program correctness.
#include <stdio.h>
static int atoi(const char *str, int n)
{
if (str == 0 || *str == 0)
return n;
return atoi(str+1, n*10 + *str-'0');
}
int main(int argc, char **argv)
{
for (int i = 1; i != argc; ++i)
printf("%s -> %d\n", argv[i], at...
Removing an item from a select box
How do I remove items from, or add items to, a select box? I'm running jQuery, should that make the task easier. Below is an example select box.
...
Rails raw SQL example
...
You can do this:
sql = "Select * from ... your sql query here"
records_array = ActiveRecord::Base.connection.execute(sql)
records_array would then be the result of your sql query in an array which you can iterate through.
...