大约有 30,000 项符合查询结果（耗时：0.0371秒） [XML]
Drop a temporary table if it exists
... IF EXISTS ##CLIENTS_KEYWORD
On previous versions you can use
IF OBJECT_ID('tempdb..##CLIENTS_KEYWORD', 'U') IS NOT NULL
/*Then it exists*/
DROP TABLE ##CLIENTS_KEYWORD
CREATE TABLE ##CLIENTS_KEYWORD
(
client_id INT
)
You could also consider truncating the table instead rather than dropping ...
MySQL和MongoDB设计实例进行对比 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...数表来单独保存。
CREATE TABLE IF NOT EXISTS `mobiles` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` VARCHAR(100) NOT NULL,
`brand` VARCHAR(100) NOT NULL,
PRIMARY KEY (`id`)
);
CREATE TABLE IF NOT EXISTS `mobile_params` (
`id` int(10) unsigned NOT NUL...
两种js滑动门(tab切换)效果 - 源码下载 - 清泛网 - 专注C/C++及内核技术
...d: #fff;
text-align: center;
margin: 0;
}
.nTab{
float: left;
width: 960px;
margin: 0 auto;
border-bottom:1px #AACCEE solid;
background:#d5d5d5;
background-position:left;
background-repeat:repeat-y;
margin-bottom:2px;
}
.nTab .TabTitle{
clear: both;
height: 22px;
ov...
how to add records to has_many :through association in rails
...mer.new(params[:customer])
@cust.houses << House.find(params[:house_id])
Or when creating a new house for a customer:
@cust = Customer.new(params[:customer])
@cust.houses.create(params[:house])
You can also add via ids:
@cust.house_ids << House.find(params[:house_id])
...
What's the difference between libev and libevent?
...ibev simply doesn't have one (for example, there is a very related library called libeio that does asynchronous I/O, which can be used independently or together with libev, so you can mix and match).
So in short, libev tries to do one thing only (POSIX event library), and this in the most efficient...
In CMake, how can I test if the compiler is Clang?
...
A reliable check is to use the CMAKE_<LANG>_COMPILER_ID variables. E.g., to check the C++ compiler:
if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
# using Clang
elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
# using GCC
elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
# using ...
Remove Primary Key in MySQL
...erty before dropping the key:
ALTER TABLE user_customer_permission MODIFY id INT NOT NULL;
ALTER TABLE user_customer_permission DROP PRIMARY KEY;
Note that you have a composite PRIMARY KEY which covers all three columns and id is not guaranteed to be unique.
If it happens to be unique, you can m...
std::vector versus std::array in C++
...ulate a dynamic array1, stored in the heap, that grows and shrinks automatically if elements are added or removed. It provides all the hooks (begin(), end(), iterators, etc) that make it work fine with the rest of the STL. It also has several useful methods that let you perform operations that on a ...
How to pull a random record using Django's ORM?
...anager):
def random(self):
count = self.aggregate(count=Count('id'))['count']
random_index = randint(0, count - 1)
return self.all()[random_index]
share
|
improve this a...
Update multiple rows in same query using PostgreSQL
... as c(column_b, column_a, column_c)
where c.column_b = t.column_b;
sql fiddle demo
share
|
improve this answer
|
follow
|
...