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updating table rows in postgres using subquery
...
Postgres allows:
UPDATE dummy
SET customer=subquery.customer,
address=subquery.address,
partn=subquery.partn
FROM (SELECT address_id, customer, address, partn
FROM /* big hairy SQL */ ...) AS subquery
WHERE dummy.addre...
Linq to Entities join vs groupjoin
...groups. This can be turned into a flat list of parent-child pairs by two small additions:
from p in parents
join c in children on p.Id equals c.Id into g // <= into
from c in g.DefaultIfEmpty() // <= flattens the groups
select new { Parent = p.Value, Child = c?.ChildValue }
The ...
Why do we need the “event” keyword while defining events?
...-like events and public fields of delegate types look similar, but are actually very different.
An event is fundamentally like a property - it's a pair of add/remove methods (instead of the get/set of a property). When you declare a field-like event (i.e. one where you don't specify the add/remove ...
Add unique constraint to combination of two columns
...ctive, PersonNumber)
VALUES(N'foo', 1, 22);
GO
Data in the table after all of this:
ID Name Active PersonNumber
---- ------ ------ ------------
1 foo 1 22
2 foo 0 22
Error message on the last insert:
Msg 2627, Level 14, State 1, Line 3
Violation of UNIQUE KEY c...
python generator “send” function purpose?
...t's useful, one of the best use cases I've seen is Twisted's @defer.inlineCallbacks. Essentially it allows you to write a function like this:
@defer.inlineCallbacks
def doStuff():
result = yield takesTwoSeconds()
nextResult = yield takesTenSeconds(result * 10)
defer.returnValue(nextResu...
When serving JavaScript files, is it better to use the application/javascript or application/x-javas
...r js in your pages, IE7 and IE8 will not run your script! Blame Microsoft all you want, but if you want most people to run your pages use text/javascript.
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Why is arr = [] faster than arr = new Array?
...BER, IDENTIFIER)
new Array: NEW, IDENTIFIER
new Array(): NEW, IDENTIFIER, CALL
new Array(5): NEW, IDENTIFIER, CALL (NUMBER)
new Array(5,4): NEW, IDENTIFIER, CALL (NUMBER, NUMBER)
new Array(5, foo): NEW, IDENTIFIER, CALL (NUMBER, IDENTIFIER)
Hopefully this should provide you a sufficient visualizat...
Is there a way to make GHC provide the type class constraints of typed holes?
...ng out-of-scope types
(use -fprint-potential-instances to see them all)
• In the expression: show _
In an equation for ‘it’: it = show _
<interactive>:3:6: error:
• Found hole: _ :: a0
Where: ‘a0’ is an ambiguous type variable
• In the first argum...
BugTrap：程序崩溃快照、bug跟踪之利器 - C/C++ - 清泛网 - 专注C/C++及内核技术
...p.h"
static void SetupExceptionHandler()
{
LOG_TRACER();
BT_InstallSehFilter();
// 配置信息
BT_SetAppName(_T("MarketInfo"));
BT_SetDialogMessage(BTDM_INTRO1, _T("We're so Sorry, program crashed because of our mistakes !"));
BT_SetDialogMessage(BTDM_INTRO2, _T("本程序...
Good examples of Not a Functor/Functor/Applicative/Monad?
...but not Applicative:
I don't have a good example. There is Const, but ideally I'd like a concrete non-Monoid and I can't think of any. All types are basically numeric, enumerations, products, sums, or functions when you get down to it. You can see below pigworker and I disagreeing about whether ...