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Update multiple rows in same query using PostgreSQL
...zable:
update test as t set
column_a = c.column_a
from (values
('123', 1),
('345', 2)
) as c(column_b, column_a)
where c.column_b = t.column_b;
You can add as many columns as you like:
update test as t set
column_a = c.column_a,
column_c = c.column_c
from (values
('123...
What is the difference between an expression and a statement in Python?
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248
Expressions only contain identifiers, literals and operators, where operators include arithmet...
How to flush output of print function?
... an optional flush argument
print("Hello world!", flush=True)
On Python 2 you'll have to do
import sys
sys.stdout.flush()
after calling print. By default, print prints to sys.stdout (see the documentation for more about file objects).
...
What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
... Wheel
This reduces the number of round-trips to the database from N+1 to 2.
Most ORM tools give you several ways to prevent N+1 selects.
Reference: Java Persistence with Hibernate, chapter 13.
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Convert light frequency to RGB?
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answered Sep 24 '09 at 15:47
Stephen MesaStephen Mesa
4,31333 gold badges2121 silver badges1616 bronze badges
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What is Func, how and when is it used
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edited Sep 2 '10 at 7:58
answered Sep 2 '10 at 7:48
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How comment a JSP expression?
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215
Pure JSP comments look like this:
<%-- Comment --%>
So if you want to retain the "="....
Python: access class property from string [duplicate]
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280
x = getattr(self, source) will work just perfectly if source names ANY attribute of self, incl...
How do I pick 2 random items from a Python set? [duplicate]
...currently have a Python set of n size where n >= 0. Is there a quick 1 or 2 lines Python solution to do it? For example, the set will look like:
...
What's the difference between `=` and `
I'm using R 2.8.1 and it is possible to use both = and <- as variable assignment operators. What's the difference between them? Which one should I use?
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