Save PL/pgSQL output from PostgreSQL to a CSV file
What is the easiest way to save PL/pgSQL output from a PostgreSQL database to a CSV file?
I'm using PostgreSQL 8.4 with pgAdmin III and PSQL plugin where I run queries from.
Do you want the resulting file on the server, or on the client?
Server side
If you want something easy to re-use or automate, you can use Postgresql's built in COPY command. eg
Copy (Select * From foo) To '/tmp/test.csv' With CSV DELIMITER ',';
This approach runs entirely on the remote server - it can't write to your local PC. It also needs to be run as a Postgres "superuser" (normally called "root") because Postgres can't stop it doing nasty things with that machine's local filesystem.
That doesn't actually mean you have to be connected as a superuser (automating that would be a security risk of a different kind), because you can use the SECURITY DEFINER option to CREATE FUNCTION to make a function which runs as though you were a superuser.
The crucial part is that your function is there to perform additional checks, not just by-pass the security - so you could write a function which exports the exact data you need, or you could write something which can accept various options as long as they meet a strict whitelist. You need to check two things:
GRANT s in the database, but the function is now running as a superuser, so tables which would normally be "out of bounds" will be fully accessible. You probably don't want to let someone invoke your function and add rows on the end of your “users” table… I've written a blog post expanding on this approach, including some examples of functions that export (or import) files and tables meeting strict conditions.
Client side
The other approach is to do the file handling on the client side , ie in your application or script. The Postgres server doesn't need to know what file you're copying to, it just spits out the data and the client puts it somewhere.
The underlying syntax for this is the COPY TO STDOUT command, and graphical tools like pgAdmin will wrap it for you in a nice dialog.
The psql command-line client has a special "meta-command" called copy , which takes all the same options as the "real" COPY , but is run inside the client:
copy (Select * From foo) To '/tmp/test.csv' With CSV
Note that there is no terminating ; , because meta-commands are terminated by newline, unlike SQL commands.
From the docs:
Do not confuse COPY with the psql instruction copy. copy invokes COPY FROM STDIN or COPY TO STDOUT, and then fetches/stores the data in a file accessible to the psql client. Thus, file accessibility and access rights depend on the client rather than the server when copy is used.
Your application programming language may also have support for pushing or fetching the data, but you cannot generally use COPY FROM STDIN / TO STDOUT within a standard SQL statement, because there is no way of connecting the input/output stream. PHP's PostgreSQL handler (not PDO) includes very basic pg_copy_from and pg_copy_to functions which copy to/from a PHP array, which may not be efficient for large data sets.
There are several solutions:
1 psql command
psql -d dbname -t -A -F"," -c "select * from users" > output.csv
This has the big advantage that you can using it via SSH, like ssh postgres@host command - enabling you to get
2 postgres copy command
COPY (SELECT * from users) To '/tmp/output.csv' With CSV;
3 psql interactive (or not)
>psql dbname
psql>f ','
psql>a
psql>o '/tmp/output.csv'
psql>SELECT * from users;
psql>q
All of them can be used in scripts, but I prefer #1.
4 pgadmin but that's not scriptable.
In terminal (while connected to the db) set output to the cvs file
1) Set field seperator to ',' :
f ','
2) Set output format unaligned:
a
3) Show only tuples:
t
4) Set output:
o '/tmp/yourOutputFile.csv'
5) Execute your query:
:select * from YOUR_TABLE
6) Output:
o
You will then be able to find your csv file in this location:
cd /tmp
Copy it using the scp command or edit using nano:
nano /tmp/yourOutputFile.csv
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