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When and why are database joins expensive?
...s back to mitigating the size of the working set. Joins involving properly selected keys with correctly set up indexes are cheap, not expensive, because they allow significant pruning of the result before the rows are materialised.
Materialising the result involves bulk disk reads which are the mo...
What is Scala's yield?
...in F# would be
[ for a in args -> a.toUpperCase ]
or
from a in args select a.toUpperCase
in Linq.
Ruby's yield has a different effect.
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IntelliJ IDEA JDK configuration on Mac OS
...Home
In IDEA you can configure the new JSDK in File | Project Structure, select SDKs on the left, then press [+] button, then specify the above JDK home path, you should get something like this:
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Table Naming Dilemma: Singular vs. Plural Names [closed]
...
Customer
Customer.CustomerID
CustomerAddress
public Class Customer {...}
SELECT FROM Customer WHERE CustomerID = 100
Once you know you are dealing with "Customer", you can be sure you will use the same word for all of your database interaction needs.
Reason 5. (Globalization). The world is gettin...
GROUP_CONCAT ORDER BY
...
You can use ORDER BY inside the GROUP_CONCAT function in this way:
SELECT li.client_id, group_concat(li.percentage ORDER BY li.views ASC) AS views,
group_concat(li.percentage ORDER BY li.percentage ASC)
FROM li GROUP BY client_id
...
How do I stop Chrome from yellowing my site's input boxes?
...e property to none.
input[type="text"], input[type="password"], textarea, select {
outline: none;
}
In cases where the browser may add a background color as well this can be fixed by something like
:focus { background-color: #fff; }
...
How do I get the collection of Model State Errors in ASP.NET MVC?
...he ModelState, use this Linq:
var modelStateErrors = this.ModelState.Keys.SelectMany(key => this.ModelState[key].Errors);
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Foreign Key to non-primary key
...int, with a scalar function checking the presence of the key:
IF EXISTS (SELECT * FROM sys.check_constraints WHERE object_id = OBJECT_ID(N'[dbo].[Check_RM_ApertureIDisValid_T_ZO_REM_AP_Raum_Reinigung]') AND parent_object_id = OBJECT_ID(N'[dbo].[T_ZO_REM_AP_Raum_Reinigung]'))
ALTER TABLE dbo.T_ZO_R...
HTML File Selection Event
...
I think @anthony is referring to the following scenario: Select a file. Now open the file selector again, but this time click on Cancel. Since no file was selected the second time, the file input control resets, thus changing its initial selection, and the change event is fired.
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jQuery: checking if the value of a field is null (empty)
... be null, it's always a string value. this isn't entirely true. I've got a select containing no options. When I perform .val() on this it returns null. Jquery 1.7.2
– Liam
Jan 14 '13 at 11:07
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