FROM lets /copy know it has to gets its data from somewhere.people(name, age) this tells Postgres we will be acting on the people table, specifically with the name and age attributes.\ copy people ( name, age ) FROM '~/Desktop/upload.csv' DELIMITER ',' CSV HEADER copy has a FROM as well as a TO, which I will demo now What we’ve covered so far is great for extracting information, but it doesn’t help with importing it. This means COPY has saved 112 lines of data. When you run the command you should see some output like COPY 112. WITH CSV DELIMITER ' ' HEADER this final part says to use CSV as the export mechanism, to use ‘ ’ as a delimiter (which just means what to use to separate the values), and finally to include a HEADER which in our case will mean the first row will have the attributes we have stored in the CSV file.Note this is going onto my local computer, in this case my Desktop, in a file called people.csv. '~/Desktop/people.csv' this is the location we want to place the output.TO is a requirement of /copy, we’ve said we want to copy something from somewhere, now we need to say TO to begin saying where we should put the data we’ve copied.It doesn’t need to be a simple query like this, any valid postgres query will work. (SELECT * FROM people) this is the data we want to copy, in our case, the result of a query./copy this tells Postgres we want to copy some information, either from somewhere or to somewhere.Lets go through each part of this line in turn This command will do the same SELECT we did earlier, but instead of displaying the data on the screen, it will export it to a CSV file. \ copy ( SELECT * FROM people ) TO '~/Desktop/people.csv' WITH CSV DELIMITER ' ' HEADER If this works you will see something like this When you run this command, Heroku will look up your app based on what you passed into the -app flag, and will find the appropriate database to connect to. The command we want to run is heroku pg:psql -app your-app-name. This tool allows you to perform Heroku actions from your command line. In Heroku, the best way to do this is with their cli tool. The first thing we need to do if we’re going to play with CSVs on Heroku databases, is actually connect to a database. This isn’t a requirement, but is incredibly useful to both machines and humans. Note the first row contains the names of the attributes we store in the CSV file. As the filename would suggest, each value is separated by a comma.īecause these are text files, and there are known standards for how they should behave, they are perfect for tools that like looping over files to send or receive data, Postgres being no exception.Ī CSV file might look something like this id, name, age What are CSV filesĬSV files, or comma separated values files are text files with a standard format. CSVs are an excellent tool for doing both of these actions. It is often the case that you need to quickly insert several rows of data into a database, or indeed export the result of a database query. ) to '~/myfile.In this post we’re going to cover how to import CSV data into a Heroku Postgres database, and export data as CSV from a Heroku Postgres database. psql -Uuser -h server2 database -c "\copy (select.In other words, this has the necessary double-quotes: However, if I try go issue that \copy (or copy) command in a single command, the output doesn't contain those double quotes, so I end up in that situation where commas in a field are interpreted as a delimiter later one. with CSV header, the file that's created is perfect, and any fields that contain a comma are automatically surrounded by double quotes. If I manually SSH from client to server 1, connect to the Postgres box, and use \copy. That psql command is hitting a Postgres server on a third machine (I can't connect directly from client to DB, hence the extra step in between). In a nutshell, I kick off my script from a client machine that uses PLINK to run a remote psql command on another box over an SSH connection. With the nature of this particular network, I have to jump through a couple of hoops to get things done, and there's a good chance I'm missing something very obvious. Trying to dump the output of a query into a CSV file in an automated job and running into an issue with fields where the column contains my comma delimiter.
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