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Tricks to manage the available memory in an R session
...
I make aggressive use of the subset parameter with selection of only the required variables when passing dataframes to the data= argument of regression functions. It does result in some errors if I forget to add variables to both the formula and the select= vector, but it sti...
MySQL: Invalid use of group function
..., not WHERE.
The difference is: the WHERE clause filters which rows MySQL selects. Then MySQL groups the rows together and aggregates the numbers for your COUNT function.
HAVING is like WHERE, only it happens after the COUNT value has been computed, so it'll work as you expect. Rewrite your subque...
Implementing Comments and Likes in database
...ucture
This pseudocode will get all the comments of photo with ID 5
SELECT * FROM actions
WHERE actions.id_Stuff = 5
AND actions.typeStuff="photo"
AND actions.typeAction = "comment"
This pseudocode will get all the likes or users who liked photo with ID 5
(you may use count() to ...
Login failed for user 'DOMAIN\MACHINENAME$'
...curity >> Logins and right click on NT AUTHORITY\NETWORK SERVICE and select Properties
In newly opened screen of Login Properties, go to the “User Mapping” tab. Then, on the “User Mapping” tab, select the desired database – especially the database for which this error message is dis...
INNER JOIN vs LEFT JOIN performance in SQL Server
...(ID, Name) VALUES (4, 'Four')
INSERT #Test2 (ID, Name) VALUES (5, 'Five')
SELECT *
FROM #Test1 t1
INNER JOIN #Test2 t2
ON t2.Name = t1.Name
SELECT *
FROM #Test1 t1
LEFT JOIN #Test2 t2
ON t2.Name = t1.Name
DROP TABLE #Test1
DROP TABLE #Test2
If you run this and view the execution plan, you'll se...
ListCtrl 重绘（Custom Draw） - C/C++ - 清泛网 - 专注C/C++及内核技术
...绘制的SubItem的Index值
l 正被绘制的Item的状态值（selected, grayed, 等等）
l Item的LPARAM值，就是你使用CListCtrl::SetItemData所设的那个值
上述所有的信息对你来说可能都很重要，这取决于你想实现什么效果，但最经常用到...
How can I define a composite primary key in SQL?
...for the table and neither value can be NULL. If you do a query like this:
SELECT * FROM voting WHERE QuestionID = 7
it will use the primary key's index. If however you do this:
SELECT * FROM voting WHERE MemberID = 7
it won't because to use a composite index requires using all the keys from th...
Doctrine - How to print out the real sql, not just the prepared statement?
...hoWriteSQLWithoutParamsLogger implements SQLLogger
{
const QUERY_TYPE_SELECT="SELECT";
const QUERY_TYPE_UPDATE="UPDATE";
const QUERY_TYPE_INSERT="INSERT";
const QUERY_TYPE_DELETE="DELETE";
const QUERY_TYPE_CREATE="CREATE";
const QUERY_TYPE_ALTER="ALTER";
private $dbPlat...
WAMP shows error 'MSVCR100.dll' is missing when install
...s://www.microsoft.com/en-us/download/details.aspx?id=30679
There you can select the x86 or x64 version depending on your system
This article on the WampServer forums shows all the Microsoft Visual C++ runtime libraries you need to have installed on your system for each version of WampServer. To ...
Extract elements of list at odd positions
...he first element (at position 0, because the indexes are 0-based) would be selected. In this case the second element will be selected.
Because the second element is omitted, the default is being used (the end of the list). So the list is being iterated from the second element to the end.
We also p...