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Oracle取前N条记录方法 Oracle实现SELECT TOP N的方法 - 爬虫/数据库 - 清...
select * from ( select * from tablexxx order by xxx desc ) where rownum <= N
oracle数据库不支持mysql中limit, top功能,但可以通过rownum来限制返回的结果集的行数,rownum并不是用户添加的字段,而是oracle系统自动添加的。
Intellij IDEA, format all code in a project
...can use the shortcut Ctrl+ALT+L (Windows/Linux) or ⌥⌘+L (MAC OS X) and select the Rearrange entries option to reformat the code in the current file or reformat a module or directory (after selecting more than one file).
You can also Right-click a module, file or directory from the context menu ...
How to map calculated properties with JPA and Hibernate
...e float finalPrice;
Or even complex queries on other tables:
@Formula("(select min(o.creation_date) from Orders o where o.customer_id = id)")
private Date firstOrderDate;
Where id is the id of the current entity.
The following blog post is worth the read: Hibernate Derived Properties - Perform...
Block commenting in Ruby
...
In TextMate, you can alt-drag vertically to select a column of text. This will duplicate the insertion point across all the lines you select, so you can insert or delete multiple #s at once.
UPDATE: Also in TextMate, assuming you have the right language selected, Cmd ...
Undo VS 'Exclude from project'?
...alled "Show All Files". To see this button, make sure that your project is selected in the solution explorer.
Show All Files
When this option is active, the file should be there, just grayed out. Right click it, and select "Include In Project".
Include In Project
...
What's the false operator in C# good for?
...he operator false declared in T, and T.&(x, y) is an invocation of the selected operator &. In other words, x is first evaluated and operator false is invoked on the result to determine if x is definitely false. Then, if x is definitely false, the result of the operation is the value previou...
SQL: IF clause within WHERE clause
... THEN '%' + @OrderNumber
ELSE ''
END
2) Use IF's outside the SELECT
IF (IsNumeric(@OrderNumber)) = 1
BEGIN
SELECT * FROM Table
WHERE @OrderNumber = OrderNumber
END ELSE BEGIN
SELECT * FROM Table
WHERE OrderNumber LIKE '%' + @OrderNumber
END
3) Using a long string, co...
How to get the index of an item in a list in a single step?
...g different (e.g. on top of any IEnumerable<>).
Use the overload of Select which takes an index in the predicate, so you transform your list into an (index, value) pair:
var pair = myList.Select((Value, Index) => new { Value, Index })
.Single(p => p.Value.Prop == oProp...
Maven in Eclipse: step by step installation [closed]
... Maven is enlisted at left panel
Finally,
Click on an existing project
Select Configure -> Convert to Maven Project
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What are C++ functors and their uses?
...te:
class SomeClass
{
std::string state_;
public:
SomeClass(const char* s) : state_(s) {}
void method( std::string param )
{
std::cout << state_ << param << std::endl;
}
};
SomeClass *inst = new SomeClass("Hi, i am ");
boost::function< void (std::st...