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PostgreSQL create table if not exists
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This feature has been implemented in Postgres 9.1:
CREATE TABLE IF NOT EXISTS myschema.mytable (i integer);
For older versions, here is a function to work around it:
CREATE OR REPLACE FUNCTION create_mytable()
RETURNS void
LANGUAGE plpgsql AS
$func$
BEGIN
IF EX...
Select multiple columns in data.table by their numeric indices
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For versions of data.table >= 1.9.8, the following all just work:
library(data.table)
dt <- data.table(a = 1, b = 2, c = 3)
# select single column by index
dt[, 2]
# b
# 1: 2
# select multiple columns by index
dt[, 2:3]
# b c
# 1: 2 3
# select ...
How can I check whether an array is null / empty?
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answered Mar 3 '10 at 9:22
cletuscletus
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How do I sort an array of hashes by a value in the hash?
... do:
sorted = sort_me.sort_by { |k| k["value"] }
puts sorted
As of Ruby 1.9+, .sort_by! is available for in-place sorting:
sort_me.sort_by! { |k| k["value"]}
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How to detect READ_COMMITTED_SNAPSHOT is enabled?
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194
SELECT is_read_committed_snapshot_on FROM sys.databases
WHERE name= 'YourDatabase'
Return va...
What do I return if the return type of a method is Void? (Not void!)
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Cactus
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answered Mar 24 '09 at 9:38
John FeminellaJohn F...
How do you get the magnitude of a vector in Numpy?
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edited Feb 1 '17 at 20:49
chutsu
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answered Fe...
Xcode can only refactor C and Objective-C code. How to rename swift class name in Xcode 6?
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NewoneNewone
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11
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How to programmatically set the layout_align_parent_right attribute of a Button in Relative Layout?
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edited May 9 '13 at 22:58
answered Jan 9 '11 at 12:04
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