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Convert text into number in MySQL query
... field,CONVERT(SUBSTRING_INDEX(field,'-',-1),UNSIGNED INTEGER) AS num
FROM table
ORDER BY num;
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How do I import a Swift file from another Swift file?
...o test then.
On newer versions of Swift it's only necessary to add the @testable keyword.
PrimeNumberModelTests.swift
import XCTest
@testable import MyProject
class PrimeNumberModelTests: XCTestCase {
let testObject = PrimeNumberModel()
}
And your internal methods can keep Internal
PrimeNu...
Difference between rake db:migrate db:reset and db:schema:load
...e creates the database
db:drop deletes the database
db:schema:load creates tables and columns within the (existing) database following schema.rb
db:setup does db:create, db:schema:load, db:seed
db:reset does db:drop, db:setup
db:migrate:reset does db:drop, db:create, db:migrate
Typically, you woul...
Does opacity:0 have exactly the same effect as visibility:hidden
...s* No No
display: none Yes No No
* Yes inside a table element, otherwise No.
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PostgreSQL ERROR: canceling statement due to conflict with recovery
... will be canceled more often.
You can work around this by starting a repeatable read transaction on primary which does a dummy query and then sits idle while a real query is run on secondary. Its presence will prevent vacuuming of old row versions on primary.
More on this subject and other workaro...
Convert a matrix to a 1 dimensional array
...dimensions of the matrix/array.
Elts_int <- as.matrix(tmp_int) # read.table returns a data.frame as Brandon noted
dim(Elts_int) <- (maxrow_int*maxcol_int,1)
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Can I use GDB to debug a running process?
...so use the "file" command
to specify the program, and to load its symbol table.
NOTE: You may have difficulty attaching to a process due to improved security in the Linux kernel - for example attaching to the child of one shell from another.
You'll likely need to set /proc/sys/kernel/yama/ptr...
Running PostgreSQL in memory only
... put the Postgres binaries into SVN (but it's more than just a single executable).
You will need to run initdb to setup your test database before you can do anything with this. This can be done from a batch file or by using Runtime.exec(). But note that initdb is not something that is fast. You wi...
setting multiple column using one update
How to set multiple columns of a table using update query in mysql?
2 Answers
2
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Convert data.frame column to a vector?
... of using the '[[' operator is that it works both with data.frame and data.table. So if the function has to be made running for both data.frame and data.table, and you want to extract a column from it as a vector then
data[["column_name"]]
is best.
...