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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...
How to copy from CSV file to PostgreSQL table with headers in CSV file?
...'','' quote ''"'' csv ', csv_file_path);
iter := 1;
col_first := (select col_1
from temp_table
limit 1);
-- update the column names based on the first row which has the column names
for col in execute format ('select unnest(string_to_array(trim(t...
Can table columns with a Foreign Key be NULL?
... otherwise an empty string can be passed as default. This is the case with MySQL, and results in an integrity error on update.
– CodeMantle
Mar 21 at 8:28
add a comment
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How do I do an OR filter in a Django query?
...ke me) where | being used as OR operator comes from, it's actually the set union operator. It's also used (not here) as bitwise OR: stackoverflow.com/questions/5988665/pipe-character-in-python
– e100
Mar 26 '15 at 18:06
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When to Redis? When to MongoDB? [closed]
...e, writing stupid sql statements... not just one but freaking everywhere. "select this, select that". But in particular you remember the irritating WHERE clause. Where lastname equals "thornton" and movie equals "bad santa." Urgh. You think, "why don’t those dbas just do their job and give me som...
detect key press in python?
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keyboard apparently requires root in linux :/
– Inaimathi
Nov 14 '17 at 16:05
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Insert a line at specific line number with sed or awk
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sed -e '8iProject_Name=sowstest' -i start using GNU sed
Sample run:
[root@node23 ~]# for ((i=1; i<=10; i++)); do echo "Line #$i"; done > a_file
[root@node23 ~]# cat a_file
Line #1
Line #2
Line #3
Line #4
Line #5
Line #6
Line #7
Line #8
Line #9
Line #10
[root@node23 ~]# sed -e '3ixxx inse...
SQL: How to get the count of each distinct value in a column?
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SELECT
category,
COUNT(*) AS `num`
FROM
posts
GROUP BY
category
share
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improve this answer
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How to specify in crontab by what user to run script? [closed]
I have few crontab jobs that run under root, but that gives me some problems. For example all folders created in process of that cron job are under user root and group root.
How can i make it to run under user www-data and group www-data so when i run scripts from my website i can manipulate those ...
NodeJS require a global module/package
...ively instead of a static path, i.e. if you are using NVM: NODE_PATH=$(npm root -g)
– holmberd
May 30 '19 at 14:05
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