大约有 42,000 项符合查询结果（耗时：0.0376秒） [XML]
Is there a way to access the “previous row” value in a SELECT statement?
...rder rows such that each one is distinct:
select rank() OVER (ORDER BY id) as 'Rank', value into temp1 from t
select t1.value - t2.value from temp1 t1, temp1 t2
where t1.Rank = t2.Rank - 1
drop table temp1
If you need to break ties, you can add as many columns as necessary to the ORDER BY.
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How to reshape data from long to wide format
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Using reshape function:
reshape(dat1, idvar = "name", timevar = "numbers", direction = "wide")
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jQuery how to find an element based on a data-attribute value?
...value of current into an Attribute Equals selector:
$("ul").find(`[data-slide='${current}']`)
For older JavaScript environments (ES5 and earlier):
$("ul").find("[data-slide='" + current + "']");
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What is SELF JOIN and when would you use it? [duplicate]
...e references data in itself.
E.g., an Employee table may have a SupervisorID column that points to the employee that is the boss of the current employee.
To query the data and get information for both people in one row, you could self join like this:
select e1.EmployeeID,
e1.FirstName,
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How do I delete rows in a data frame?
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The key idea is you form a set of the rows you want to remove, and keep the complement of that set.
In R, the complement of a set is given by the '-' operator.
So, assuming the data.frame is called myData:
myData[-c(2, 4, 6), ] ...
Storyboard - refer to ViewController in AppDelegate
consider the following scenario: I have a storyboard-based app. I add a ViewController object to the storyboard, add the class files for this ViewController into the project and specify the name of the new class in the IB identity inspector. Now how am I going to refer to this ViewController program...
Postgresql query between date ranges
... simpler if you use >= start AND < end.
For example:
SELECT
user_id
FROM
user_logs
WHERE
login_date >= '2014-02-01'
AND login_date < '2014-03-01'
In this case you still need to calculate the start date of the month you need, but that should be straight forward in any num...
Set title background color
In my android application I want the standard/basic title bar to change color.
13 Answers
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Using 'starts with' selector on individual class names
... using space in there. Can one use boolean operators in a jquery selector? Ideally, the above would be 'OR' to avoid the (rare and likely avoidable) case where there are more than one class staring with 'apple-'
– DA.
Feb 1 '10 at 17:12
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How can I create a copy of an object in Python?
...elf)(self.a, self.b)
def __deepcopy__(self, memo): # memo is a dict of id's to copies
id_self = id(self) # memoization avoids unnecesary recursion
_copy = memo.get(id_self)
if _copy is None:
_copy = type(self)(
deepcopy(self.a, memo),
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