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How to use GROUP BY to concatenate strings in MySQL?
...aracters, so we first do:
SET group_concat_max_len=100000000;
and then, for example:
SELECT pub_id,GROUP_CONCAT(cate_id SEPARATOR ' ') FROM book_mast GROUP BY pub_id
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Convert column classes in data.table
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For a single column:
dtnew <- dt[, Quarter:=as.character(Quarter)]
str(dtnew)
Classes ‘data.table’ and 'data.frame': 10 obs. of 3 variables:
$ ID : Factor w/ 2 levels "A","B": 1 1 1 1 1 2 2 2 2 2
$ Quarter: c...
XPath to find elements that does not have an id or class
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Pretty straightforward:
//tr[not(@id) and not(@class)]
That will give you all tr elements lacking both id and class attributes. If you want all tr elements lacking one of the two, use or instead of and:
//tr[not(@id) or not(@class)]
W...
When to use Comparable and Comparator
...e sorting was an unusual use of the class, or the sorting only makes sense for a specific use case, then a Comparator is a better option.
Put another way, given the class name, is it clear how a comparable would sort, or do you have to resort to reading the javadoc? If it is the latter, odds are ev...
Update Row if it Exists Else Insert Logic with Entity Framework
...ooks like what I need. Can I ask you one question that's been bothering me for a while? Normally, I put my context in a short using block. Is it okay to leave the context in memory for a while? For example, during the life of a Windows form? I normally try and clean up database objects to ensure min...
Do AJAX requests retain PHP Session info?
...page request. They are both HTTP requests, and they both contain cookie information in the header in the same way.
From the client side, the same cookies will always be sent to the server whether it's a regular request or an AJAX request. The Javascript code does not need to do anything special o...
The object cannot be deleted because it was not found in the ObjectStateManager
...y Framework?. You are right, this seems to be the issue in my case. Thanks for the quick answer!
– Matt
Sep 6 '13 at 10:44
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Rails where condition using NOT NIL
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Last one here isn't working for me, do we need an extra gem or plugin for this? I get: rails undefined method 'not_eq' for :confirmed_at:Symbol..
– Tim Baas
Jun 7 '11 at 10:21
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jquery if div id has children
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Thanks for the answer. This is is what worked for me. I knew I was on the right track with the .children(), but didn't know what was wrong with it. Apparently size could be 0, makes sense.
– Chris
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iPhone get SSID without private library
... of the network it is connected to: If it is connected to a Adhoc network for a 3rd party hardware device it needs to be functioning in a different manner than if it is connected to the internet.
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