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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
...
How do you use variables in a simple PostgreSQL script?
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Here's an example of using a variable in plpgsql:
create table test (id int);
insert into test values (1);
insert into test values (2);
insert into test values (3);
create function test_fn() returns int as $$
declare val int := 2;
begin
return (SELECT id FROM test ...
sql primary key and index
...ou may reach the desired optimization for a query.
For example you have a table with many columns but you are only querying ID, Name and Address columns. Taking ID as the primary key, we can create the following index that is built on ID but includes Name and Address columns.
CREATE NONCLUSTERED I...
UITableView row animation duration and completion callback
Is there a way to either specify the duration for UITableView row animations, or to get a callback when the animation completes?
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List of ANSI color escape sequences
... underlined (4) and the last part clears all this (0).
As described in the table below, there are a large number of text properties you can set, such as boldness, font, underlining, &c. (Isn't it silly that StackOverflow doesn't allow you to put proper tables in answers?)
Font Effects
╔══...
How to make an image center (vertically & horizontally) inside a bigger div [duplicate]
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another way is to create a table with valign, of course. This would work regardless of you knowing the div's height or not.
<div>
<table width="100%" height="100%" align="center" valign="center">
<tr><td>
<img sr...
How to create a printable Twitter-Bootstrap page
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Bootstrap 3.2 update: (current release)
Current stable Bootstrap version is 3.2.0.
With version 3.2 visible-print deprecated, so you should use like this:
Class Browser Print
-------------------------------------------------
.visible-print-block ...
How to Implement Custom Table View Section Headers and Footers with Storyboard
...simply drag a UIView onto the canvas, lay it out and then set it in the tableView:viewForHeaderInSection or tableView:viewForFooterInSection delegate methods.
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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...
ActiveRecord OR query
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Use ARel
t = Post.arel_table
results = Post.where(
t[:author].eq("Someone").
or(t[:title].matches("%something%"))
)
The resulting SQL:
ree-1.8.7-2010.02 > puts Post.where(t[:author].eq("Someone").or(t[:title].matches("%something%"))).to_...