大约有 6,888 项符合查询结果（耗时：0.0335秒） [XML]
Best way to test if a row exists in a MySQL table
...on in the comments, that in this situation:
SELECT 1 FROM my_table WHERE *indexed_condition* LIMIT 1
Is superior to:
SELECT * FROM my_table WHERE *indexed_condition* LIMIT 1
This is because the first query can be satisfied by the index, whereas the second requires a row look up (unless possibl...
MySQL case insensitive select
...e, comparisons are case-insensitive. You need to understand collations and indexes and configure those properly - using string transformations like LOWER() or an arbitrary COLLATE clause can completely bypass an index, and over time, as your table grows, this can have drastic performance implication...
Difference between partition key, composite key and clustering key in Cassandra?
...y in the order they're set.
so the valid queries are (excluding secondary indexes)
col1 and col2
col1 and col2 and col10
col1 and col2 and col10 and col 4
Invalid:
col1 and col2 and col4
anything that does not contain both col1 and col2
Hope this helps.
...
HashSet vs. List performance
... List potentially might calculate offset for the specific element by it's index (because all elements are the same type and potentially occupy same memory size). So List is not necessary enumerates it's elements
– Lu55
Oct 21 '14 at 11:54
...
How do I Sort a Multidimensional Array in PHP [duplicate]
...
foreach ($mdarray as $key => $row) {
// replace 0 with the field's index/key
$dates[$key] = $row[0];
}
array_multisort($dates, SORT_DESC, $mdarray);
For PHP >= 5.5.0 just extract the column to sort by. No need for the loop:
array_multisort(array_column($mdarray, 0), SORT_DESC, $...
TypeScript Objects as Dictionary types as in C#
... That's a useful way to make sure that the compiler restricts indexes to strings. Interesting. Doesn't look like you can specify the index type to be anything other than strings or integers, but that makes sense, since it just maps to the native JS object indexes.
–...
WAMP 403 Forbidden message on Windows 7
...onf (Apache's config file) :
<Directory "c:/wamp/www/">
Options Indexes FollowSymLinks
AllowOverride all
Order Deny,Allow
Deny from all
Allow from 127.0.0.1
</Directory>
The same goes for your PHPMyAdmin access, the config file is phpmyadmin.conf :
<Directory "...
Elegant solution to duplicate, const and non-const, getters? [duplicate]
...bout:
template<typename IN, typename OUT>
OUT BigChunk(IN self, int index) {
// big, non-trivial chunk of code...
return something;
}
struct FooBar {
Something &getSomething(int index) {
return BigChunk<FooBar*, Something&>(this,index);
}
const Some...
Remove the last three characters from a string
...ly asked question]
You can use string.Substring and give it the starting index and it will get the substring starting from given index till end.
myString.Substring(myString.Length-3)
Retrieves a substring from this instance. The substring starts at a
specified character position. MSDN
E...
How do I undo 'git add' before commit?
... commit with
git reset <file>
which will remove it from the current index (the "about to be committed" list) without changing anything else.
You can use
git reset
without any file name to unstage all due changes. This can come in handy when there are too many files to be listed one by one in...