大约有 7,000 项符合查询结果（耗时：0.0163秒） [XML]
Is storing a delimited list in a database column really that bad?
...ient table-scan. May have to resort to regular expressions, for example in MySQL:
idlist REGEXP '[[:<:]]2[[:>:]]'*
Hard to count elements in the list, or do other aggregate queries.
Hard to join the values to the lookup table they reference.
Hard to fetch the list in sorted order.
To solve th...
How can I implement a tree in Python?
... self.right = None
self.data = None
You can use it like this:
root = Tree()
root.data = "root"
root.left = Tree()
root.left.data = "left"
root.right = Tree()
root.right.data = "right"
If you need an arbitrary number of children per node, then use a list of children:
class Tree:
def...
Rails Root directory path?
How do I get my Rails app's root directory path?
9 Answers
9
...
What is sharding and why is it important?
...cross multiple logical or physical nodes (in the case of my understanding (mySQL) multiple databases, most likely housed on different logical hardware). Horizontal partitioning is a less specific term, of which "Sharding" is a subset. Again using mySQL as an example, a mySQL partition is handled by...
Subqueries vs joins
...
Here's an example of how subqueries are evaluated in MySQL 6.0.
The new optimizer will convert this kind of subqueries into joins.
share
|
improve this answer
|
...
Select something that has more/less than x character
...nks.
Here's the link to the MSDN
For oracle/plsql you can use Length(), mysql also uses Length.
Here is the Oracle documentation:
http://www.techonthenet.com/oracle/functions/length.php
And here is the mySQL Documentation of Length(string):
http://dev.mysql.com/doc/refman/5.1/en/string-functi...
What's an Aggregate Root?
...o properly use the repository pattern. The central concept of an Aggregate Root keeps coming up. When searching both the web and Stack Overflow for help with what an aggregate root is, I keep finding discussions about them and dead links to pages that are supposed to contain base definitions.
...
When NOT to use Cassandra?
...ase of RDBMS, making a choice is quite easy because all the databases like MySQL, Oracle, MS SQL, PostgreSQL in this category offer almost the same kind of solutions oriented toward ACID properties. When it comes to NoSQL, the decision becomes difficult because every NoSQL database offers different ...
Nginx — static file serving confusion with root & alias
...nswers to my confusions.
There is a very important difference between the root and the alias directives. This difference exists in the way the path specified in the root or the alias is processed.
In case of the root directive, full path is appended to the root including the location part, whereas...
Why do I get access denied to data folder when using adb?
... want to browse everything on your device.
You need to have a phone with root access in order to browse the data folder on an Android phone. That means either you have a developer device (ADP1 or an ION from Google I/O) or you've found a way to 'root' your phone some other way.
You need to be runn...