大约有 40,000 项符合查询结果（耗时：0.0176秒） [XML]
#pragma pack effect
...B(3) | BB(4) |
| CC(1) | pad.. |
And sizeof(Test) would be 2 × 4 = 8.
Order of variables in struct is also important. With variables ordered like following:
struct Test
{
char AA;
char CC;
int BB;
};
and with #pragma pack(2), the struct would be laid out like this:
| 1 | 2 ...
MySQL INNER JOIN select only one row from second table
... = (
SELECT id
FROM payments AS p2
WHERE p2.user_id = u.id
ORDER BY date DESC
LIMIT 1
)
Or
SELECT u.*, p.*
FROM users AS u
INNER JOIN payments AS p ON p.user_id = u.id
WHERE NOT EXISTS (
SELECT 1
FROM payments AS p2
WHERE
p2.user_id = p.user_id AND
(p...
Can you do greater than comparison on a date in a Rails 3 search?
...er.id, :notetype => p[:note_type]).
where("date > ?", p[:date]).
order('date ASC, created_at ASC')
or you can also convert everything into the SQL notation
Note.
where("user_id = ? AND notetype = ? AND date > ?", current_user.id, p[:note_type], p[:date]).
order('date ASC, created...
Reusable library to get human readable version of file size?
...came up with a version that avoids loops, using log2 to determine the size order which doubles as a shift and an index into the suffix list:
from math import log2
_suffixes = ['bytes', 'KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB']
def file_size(size):
# determine binary order in ste...
Hashing a dictionary?
...
@Ceaser That won't work because tuple implies ordering but dict items are unordered. frozenset is better.
– Antimony
Jul 30 '12 at 11:55
28
...
map vs. hash_map in C++
...
They are implemented in very different ways.
hash_map (unordered_map in TR1 and Boost; use those instead) use a hash table where the key is hashed to a slot in the table and the value is stored in a list tied to that key.
map is implemented as a balanced binary search tree (usuall...
__lt__ instead of __cmp__
...
TypeError: Cannot create a consistent method resolution order (MRO) for bases object, ComparableMixin when I try this in Python 3. See the full code at gist.github.com/2696496
– Adam Parkin
May 14 '12 at 20:23
...
How to query as GROUP BY in django?
... @Gidgidonihah True, the example should read Members.objects.order_by('disignation').values('designation').annotate(dcount=Count('designation'))
– bjunix
Oct 30 '14 at 15:16
...
Difference between TCP and UDP?
...guarantees that all sent packets will reach the destination in the correct order. This imply the use of acknowledgement packets sent back to the sender, and automatic retransmission, causing additional delays and a general less efficient transmission than UDP.
UDP is a connection-less protocol. Com...
Get the first key name of a javascript object [duplicate]
..." key in a hash (Javascript calls them objects). They are fundamentally unordered. Do you mean just choose any single key:
for (var k in ahash) {
break
}
// k is a key in ahash.
share
|
imp...