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Does Foreign Key improve query performance?
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foreign keys do improve performance, at least in MySQL. Moreover, you're right, the creation of a FK does not create an index; the creation of a FK requires an index
– Félix Gagnon-Grenier
Aug 26 '14 at 17:31
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IntelliJ does not show 'Class' when we right click and select 'New'
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The directory or one of the parent directories must be marked as Source Root (In this case, it appears in blue).
If this is not the case, right click your root source directory -> Mark As -> Source Root.
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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...
can we use xpath with BeautifulSoup?
... One warning: I've noticed if there is something outside the root (like a \n outside the outer <html> tags), then referencing xpaths by the root will not work, you have to use relative xpaths. lxml.de/xpathxslt.html
– wordsforthewise
Sep 6 '...
Outputting data from unit test in python
...og.debug() next to each other, and explicitly turn on DEBUG logging at the root from the setUp() method, but only the print output shows up.
– haridsv
Nov 15 '11 at 2:04
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How to copy from CSV file to PostgreSQL table with headers in CSV file?
...because it uses native DB import commands. It supports Postgres as well as MYSQL and MS SQL.
import pandas as pd
df = pd.read_csv('table.csv')
uri_psql = 'postgresql+psycopg2://usr:pwd@localhost/db'
d6tstack.utils.pd_to_psql(df, uri_psql, 'table')
It is also useful for importing multiple CSVs, so...
How to run a PowerShell script from a batch file
... answered Mar 29 '14 at 19:38
Root LoopRoot Loop
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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
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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...
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 ...