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Multiple INSERT statements vs. single INSERT with multiple VALUES
...ng the number of VALUES clauses and recording the compile time.
I then divided the compile time by the number of rows to get the average compile time per clause. The results are below
Up until 250 VALUES clauses present the compile time / number of clauses has a slight upward trend but nothing t...
Java - JPA - @Version annotation
...operty:
@Entity
public class MyEntity implements Serializable {
@Id
@GeneratedValue
private Long id;
private String name;
@Version
private Long version;
//...
}
On update, the field annotated with @Version will be incremented and added to the WHERE clause, some...
Remove rows with all or some NAs (missing values) in data.frame
...
tidyr has a new function drop_na:
library(tidyr)
df %>% drop_na()
# gene hsap mmul mmus rnor cfam
# 2 ENSG00000199674 0 2 2 2 2
# 6 ENSG00000221312 0 1 2 3 2
df %>% drop_na(rn...
Remove last item from array
...n.js"></script>
<b>Original Array : </b>
<div id="div1"></div>
<br/>
<b>After slice(0, -1): </b>
<div id="div2"></div>
instead of doing :
arr.slice(-1); // returns [2]
Here is a demo:
var arr = [1, 0, 2];
var ne...
What is the difference between “INNER JOIN” and “OUTER JOIN”?
...ally show any distinction between different types of join predicate or provide a framework for reasoning about how they will operate.
There is no substitute for understanding the logical processing and it is relatively straightforward to grasp anyway.
Imagine a cross join.
Evaluate the on clause ag...
Paging with Oracle
... a.*, rownum r__
FROM
(
SELECT * FROM ORDERS WHERE CustomerID LIKE 'A%'
ORDER BY OrderDate DESC, ShippingDate DESC
) a
WHERE rownum < ((pageNumber * pageSize) + 1 )
)
WHERE r__ >= (((pageNumber-1) * pageSize) + 1)
...
Converting XML to JSON using Python?
... some understanding of what you want to do with the results.
That being said, Python's standard library has several modules for parsing XML (including DOM, SAX, and ElementTree). As of Python 2.6, support for converting Python data structures to and from JSON is included in the json module.
So th...
How can I put a database under git (version control)?
...ou make the new schema changes to and not touch the old one since as you said you are making a branch.
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How to tag an older commit in Git?
...eb02 -m "Message here"
Where 9fceb02 is the beginning part of the commit id.
You can then push the tag using git push origin v1.2.
You can do git log to show all the commit id's in your current branch.
There is also a good chapter on tagging in the Pro Git book.
Warning: This creates tags with...
How can i tell if an object has a key value observer attached
...{
[someObject removeObserver:someObserver forKeyPath:somePath];
}@catch(id anException){
//do nothing, obviously it wasn't attached because an exception was thrown
}
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