大约有 40,000 项符合查询结果（耗时：0.0467秒） [XML]
Is gcc std::unordered_map implementation slow? If so - why?
...red_map, the g++ implementation will automatically rehash to a larger hash table, and this would be a big drag on performance. If I remember correctly, unordered_map defaults to (smallest prime larger than) 100.
I didn't have chrono on my system, so I timed with times().
template <typename TEST...
How to set Sqlite3 to be case insensitive when string comparing?
... can indicate that a column should be case insensitive when you create the table by specifying collate nocase in the column definition (the other options are binary (the default) and rtrim; see here). You can specify collate nocase when you create an index as well. For example:
create table Test...
What is the difference between MOV and LEA?
...is answer is basically wrong because the question is asking about MOV AX, [TABLE-ADDR], which is a load. So there is a major difference. The equivalent instruction is mov ax, OFFSET table_addr
– Peter Cordes
Feb 27 '18 at 23:56
...
Why is there extra padding at the top of my UITableView with style UITableViewStyleGrouped in iOS7
Starting in iOS7, there is additional space at the top of my UITableView 's which have a style UITableViewStyleGrouped .
...
The difference between fork(), vfork(), exec() and clone()
...s big. I presume this is because the kernel still has to copy all the page tables.
– Martina Ferrari
Mar 15 '16 at 3:04
4
...
How can prepared statements protect from SQL injection attacks?
...SELECT * FROM users where id=1
while this code
$spoiled_data = "1; DROP TABLE users;"
$query = "SELECT * FROM users where id=$spoiled_data";
will produce a malicious sequence
SELECT * FROM users where id=1; DROP TABLE users;
It works because we are adding the data directly to the prog...
MySQL: Transactions vs Locking Tables
I'm a bit confused with transactions vs locking tables to ensure database integrity and make sure a SELECT and UPDATE remain in sync and no other connection interferes with it. I need to:
...
Setting element of array from Twig
...That will work only when keys are strings
What I did is recreate another table ( temp) from the initial table (t) and make the keys a string , for example :
{% for key , value in t%}
{% set temp= temp|merge({(key~'_'):value}) %}
{% endfor %}
t keys : 0 , 1 , 2 ..
temp keys : 0_, 1_ , 2_ ......
Set value to NULL in MySQL
...t NULL inside quotes in your update statement. This should work:
UPDATE table SET field = NULL WHERE something = something
share
|
improve this answer
|
follow
...
I need to generate uuid for my rails application. What are the options(gems) I have? [duplicate]
... the column.
Example in Rails 3 migration
execute <<-SQL
CREATE TABLE some_items (id uuid PRIMARY KEY DEFAULT uuid_generate_v1());
SQL
Might be a better way to do this in Rails 4.
share
|
...