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Database Structure for Tree Data Structure
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Have a look at Managing Hierarchical Data in MySQL. It discusses two approaches for storing and managing hierarchical (tree-like) data in a relational database.
The first approach is the adjacency list model, which is what you essentially describe: having a foreign key...
In Docker, what's the difference between a container and an image? [duplicate]
...o give us an interactive bash shell.
$ docker run -i -t ubuntu /bin/bash
root@48cff2e9be75:/# ls
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
root@48cff2e9be75:/# cat > foo
This is a really important file!!!!
root@48cff2e9be75:/# exit
...
Best practices for Storyboard login screen, handling clearing of data upon logout
I'm building an iOS app using a Storyboard. The root view controller is a Tab Bar Controller. I'm creating the login/logout process, and it's mostly working fine, but I've got a few issues. I need to know the BEST way to set all this up.
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Why does the order in which libraries are linked sometimes cause errors in GCC?
...llowing scenario:
myprog.o - containing main() function, dependent on libmysqlclient
libmysqlclient - static, for the sake of the example (you'd prefer the shared library, of course, as the libmysqlclient is huge); in /usr/local/lib; and dependent on stuff from libz
libz (dynamic)
How do we link...
Update all values of a column to lowercase
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See http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_lower
UPDATE table_name SET tag = LOWER(tag)
share
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improve t...
How to validate an e-mail address in swift?
... user@host without .tld is also a valid email address, e.g. root@localhost
– Wed
Feb 9 '18 at 15:21
1
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What is __pycache__?
...all of these folders in your project by running following command from the root folder of your project.
find . -name '__pycache__' -exec chflags hidden {} \;
Replace __pycache__ with *.pyc for Python 2.
This sets a flag on all those directories (.pyc files) telling Finder/Textmate 2 to exclude ...
Django 1.7 throws django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet
...This works for me for Django 1.9 . The Python script to execute was in the root of the Django project.
import django
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "PROJECT_NAME.settings")
django.setup()
from APP_NAME.models import *
Set PROJECT_NAME and APP_NAME to yours
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Mechanisms for tracking DB schema changes [closed]
...se.
Make a backup of the current database (because stuff will go wrong) [mysqldump].
Create bookkeeping table (called _meta) if it doesn't exist.
Read current VERSION from _meta table. Assume 0 if not found.
For all .sql files numbered higher than VERSION, execute them in order
If one of t...
Why all the Active Record hate? [closed]
...database itself, tables, relations, even some logic if the DBMS allows it (MySQL is also grown-up now)
A2) very often, there is more than a data store: file system (blobs in database are not always a good decision...), legacy systems (imagine yourself "how" they will be accessed, many varieties pos...