大约有 48,000 项符合查询结果（耗时：0.0285秒） [XML]
“Cannot evaluate expression because the code of the current method is optimized” in Visual Studio 20
...this issue when I was using VS 2010. My solution configuration has (Debug) selected. I resolved this by unchecking the Optimize Code property under project properties.
Project (right Click)=> Properties => Build (tab) => uncheck Optimize code
...
Transaction isolation levels relation with locks on table
... writes data and commit/rollback (depending on results). B just executes a SELECT statement to read data. C reads and updates data. All these process work on the same table T.
READ UNCOMMITTED - no lock on the table. You can read data in the table while writing on it. This means A writes data (unc...
How to get last N records with activerecord?
...e-wise - at least not up to Rails 3.1. SomeModel.last(5) will execute the select statement without a limit, returning all records of SomeModel to Ruby as an array, after which Ruby will pick out the last (5) elements. Efficiency-wise, currently, you want to use limit - particularly if you have pote...
How to select html nodes by ID with jquery when the id contains a dot?
...
@Tomalak in comments:
since ID selectors must be preceded by a hash #, there should be no ambiguity here
“#id.class” is a valid selector that requires both an id and a separate class to match; it's valid and not always totally redundant.
The correct...
Is there a MySQL option/feature to track history of changes to records?
...i AFTER INSERT ON MyDB.data FOR EACH ROW
INSERT INTO MyDB.data_history SELECT 'insert', NULL, NOW(), d.*
FROM MyDB.data AS d WHERE d.primary_key_column = NEW.primary_key_column;
CREATE TRIGGER MyDB.data__au AFTER UPDATE ON MyDB.data FOR EACH ROW
INSERT INTO MyDB.data_history SELECT 'up...
Best approach to real time http streaming to HTML5 video client
...for the detailed background and pro/cons about the various options. I have selected this answer as the accepted one as the outline of the concepts are more important than the specific fix which I found to answer the original question. Good luck with the bounty!
– deandob
...
LINQ's Distinct() on a particular property
...
(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
HashSet<TKey> seenKeys = new HashSet<TKey>();
foreach (TSource element in source)
{
if (seenKeys.Add(keySelector(element)))
{
yield return element;
}
...
Is there a JSON equivalent of XQuery/XPath?
...g
tools including filtering, recursive search, sorting, mapping, range
selection, and flexible expressions with wildcard string comparisons
and various operators.
JSONselect has another point of view on the question (CSS selector-like, rather than XPath) and has a JavaScript implementation.
...
Can't launch my app in Instruments: At least one target failed to launch
...To change your code signing identity for Xcode 6:
Click on your Project, Select the Target you are Profiling.
Build Settings -> Code Signing -> Code Signing Identity -> Release
Select your iOS developer profile.
Provisioning Profile: Let Xcode pick the correct Provisioning Profile for yo...
MySQL show current connection info
...e are MYSQL functions you can use. Like this one that resolves the user:
SELECT USER();
This will return something like root@localhost so you get the host and the user.
To get the current database run this statement:
SELECT DATABASE();
Other useful functions can be found here: http://dev.mys...