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Advantages and disadvantages of GUID / UUID database keys
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@Matt Sheppard:
Say you have a table of customers. Surely you don't want a customer to exist in the table more than once, or lots of confusion will happen throughout your sales and logistics departments (especially if the multiple rows about the customer c...
How to understand nil vs. empty vs. blank in Ruby
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I made this useful table with all the cases:
blank?, present? are provided by Rails.
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SQLite: How do I save the result of a query as a CSV file?
...ex = False)
You can customize the query to only export part of the sqlite table to the CSV file.
You can also run a single command to export all sqlite tables to CSV files:
for table in c.execute("SELECT name FROM sqlite_master WHERE type='table';").fetchall():
t = table[0]
df = pd.read_sql...
Changing column names of a data frame
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Try setnames() in the data.table package. Use something like setnames(DT,"b","B") or setnames(DT,c("a","E"),c("A","F"))
– dwstu
Aug 11 '14 at 17:23
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LINQ-to-SQL vs stored procedures? [closed]
...umber of supported databases will only increase. Sprocs are not always portable between databases, either because of varying syntax or feature support (if the database supports sprocs at all).
Deployment: Others have mentioned this already, but it's easier to deploy a single assembly than to deploy...
How to include “zero” / “0” results in COUNT aggregate?
...u want an outer join for this (and you need to use person as the "driving" table)
SELECT person.person_id, COUNT(appointment.person_id) AS "number_of_appointments"
FROM person
LEFT JOIN appointment ON person.person_id = appointment.person_id
GROUP BY person.person_id;
The reason why this is wo...
Best Practices: Salting & peppering passwords?
...n order for it to be considered secure. Additionally, it has to be implementable in a maintainable way. The most secure system that can't be maintained is considered insecure (because if any part of that security breaks down, the entire system falls apart).
And peppers fit neither the provable or t...
Select all 'tr' except the first one
How can I select all tr elements except the first tr in a table with CSS?
10 Answers
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Django migration strategy for renaming a model and relationship fields
...different name, and the migration it creates will lose any data in the old table." Django 2.1 Docs For me, it was sufficient to create an empty migration, add the model renames to it, then run makemigrations as usual.
– hlongmore
Jan 15 '19 at 9:05
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Should I commit or rollback a read transaction?
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Suppose I create a temp table, populate it with ids, join it with a data table to select the data that goes with the ids, then delete the temp table. I'm really just reading data, and I don't care what happens to the temp table, since it's temporar...