大约有 40,000 项符合查询结果（耗时：0.0507秒） [XML]
SQL: IF clause within WHERE clause
...n a WHERE clause. If you want to apply some "IF" logic in the WHERE clause all you need to do is add the extra condition with an boolean AND to the section where it needs to be applied.
share
|
impr...
Thou shalt not inherit from std::vector
Ok, this is really difficult to confess, but I do have a strong temptation at the moment to inherit from std::vector .
13...
What is the difference between pluck and collect in Rails?
...
When you do:
User.first.gifts.collect(&:id)
You have objects with all fields loaded and you simply get the id thanks to the method based on Enumerable.
So:
if you only need the id with Rails 4, use ids: User.first.gifts.ids
if you only need some fields with Rails 4, use pluck: User.first...
Change Volley timeout duration
...requests.
Volley sets default Socket & ConnectionTImeout to 5 secs for all requests.
RetryPolicy is an interface where you need to implement your logic of how you want to retry a particular request when a timeout happens.
It deals with these three parameters
Timeout - Specifies Socket Timeo...
When should I use a struct instead of a class?
...
MSDN has the answer:
Choosing Between Classes and Structures.
Basically, that page gives you a 4-item checklist and says to use a class unless your type meets all of the criteria.
Do not define a structure unless the
type has all of the following
characteristics:
It logica...
Flexbox not giving equal width to elements
...t has up to 5 items and as little as 3, but it's not dividing the width equally between all the elements.
2 Answers
...
Why doesn't Ruby support i++ or i-- (increment/decrement operators)?
...ct the variable references with a whole new object. You can check this by calling i.object_id before and after i+=1. Why would that be any more technically tricky to do with ++?
– Andy_Vulhop
Sep 7 '10 at 17:09
...
MySQL ON vs USING?
... far as I can tell, USING() is just more convenient syntax, whereas ON allows a little more flexibility when the column names are not identical. However, that difference is so minor, you'd think they'd just do away with USING() .
...
How to get maximum value from the Collection (for example ArrayList)?
...f the given collection, according to the natural ordering of its elements. All elements in the collection must implement the Comparable interface.
share
|
improve this answer
|
...
When to add what indexes in a table in Rails
...
Should I add "index" to all the foreign keys like "xxx_id"?
It would be better, because it accelerates the search in sorting in this column. And Foreign keys are something searched for a lot.
Since Version 5 of rails the index will be created aut...