Save PL/pgSQL output from PostgreSQL to a CSV file

问题:

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.

回答1:

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. e.g.

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:

1. Which files should the user be allowed to read/write on disk? This might be a particular directory, for instance, and the filename might have to have a suitable prefix or extension.
2. Which tables should the user be able to read/write in the database? This would normally be defined by GRANTs 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.

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Client side

The other approach is to do the file handling on the client side, i.e. 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.

回答2:

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.

回答3:

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

回答4:

If you\'re interested in all the columns of a particular table along with headers, you can use

COPY table TO \'/some_destdir/mycsv.csv\' WITH CSV HEADER;

This is a tiny bit simpler than

COPY (SELECT * FROM table) TO \'/some_destdir/mycsv.csv\' WITH CSV HEADER;

which, to the best of my knowledge, are equivalent.

回答5:

I had to use the \\COPY because I received the error message:

ERROR:  could not open file \"/filepath/places.csv\" for writing: Permission denied

So I used:

\\Copy (Select address, zip  From manjadata) To \'/filepath/places.csv\' With CSV;

and it is functioning

回答6:

psql can do this for you:

edd@ron:~$ psql -d beancounter -t -A -F\",\" \\
                -c \"select date, symbol, day_close \" \\
                   \"from stockprices where symbol like \'I%\' \" \\
                   \"and date >= \'2009-10-02\'\"
2009-10-02,IBM,119.02
2009-10-02,IEF,92.77
2009-10-02,IEV,37.05
2009-10-02,IJH,66.18
2009-10-02,IJR,50.33
2009-10-02,ILF,42.24
2009-10-02,INTC,18.97
2009-10-02,IP,21.39
edd@ron:~$

See man psql for help on the options used here.

回答7:

CSV Export Unification

This information isn\'t really well represented. As this is the second time I\'ve needed to derive this, I\'ll put this here to remind myself if nothing else.

Really the best way to do this (get CSV out of postgres) is to use the COPY ... TO STDOUT command. Though you don\'t want to do it the way shown in the answers here. The correct way to use the command is:

COPY (select id, name from groups) TO STDOUT WITH CSV HEADER

Remember just one command!

It\'s great for use over ssh:

$ ssh psqlserver.example.com \'psql -d mydb \"COPY (select id, name from groups) TO STDOUT WITH CSV HEADER\"\' > groups.csv

It\'s great for use inside docker over ssh:

$ ssh pgserver.example.com \'docker exec -tu postgres postgres psql -d mydb -c \"COPY groups TO STDOUT WITH CSV HEADER\"\' > groups.csv

It\'s even great on the local machine:

$ psql -d mydb -c \'COPY groups TO STDOUT WITH CSV HEADER\' > groups.csv

Or inside docker on the local machine?:

docker exec -tu postgres postgres psql -d mydb -c \'COPY groups TO STDOUT WITH CSV HEADER\' > groups.csv

Or on a kubernetes cluster, in docker, over HTTPS??:

kubectl exec -t postgres-2592991581-ws2td \'psql -d mydb -c \"COPY groups TO STDOUT WITH CSV HEADER\"\' > groups.csv

So versatile, much commas!

Do you even?

Yes I did, here are my notes:

The COPYses

Using /copy effectively executes file operations on whatever system the psql command is running on, as the user who is executing it1. If you connect to a remote server, it\'s simple to copy data files on the system executing psql to/from the remote server.

COPY executes file operations on the server as the backend process user account (default postgres), file paths and permissions are checked and applied accordingly. If using TO STDOUT then file permissions checks are bypassed.

Both of these options require subsequent file movement if psql is not executing on the system where you want the resultant CSV to ultimately reside. This is the most likely case, in my experience, when you mostly work with remote servers.

It is more complex to configure something like a TCP/IP tunnel over ssh to a remote system for simple CSV output, but for other output formats (binary) it may be better to /copy over a tunneled connection, executing a local psql. In a similar vein, for large imports, moving the source file to the server and using COPY is probably the highest-performance option.

PSQL Parameters

With psql parameters you can format the output like CSV but there are downsides like having to remember to disable the pager and not getting headers:

$ psql -P pager=off -d mydb -t -A -F\',\' -c \'select * from groups;\'
2,Technician,Test 2,,,t,,0,,                                                                                                                                                                   
3,Truck,1,2017-10-02,,t,,0,,                                                                                                                                                                   
4,Truck,2,2017-10-02,,t,,0,,

Other Tools

No, I just want to get CSV out of my server without compiling and/or installing a tool.

回答8:

In pgAdmin III there is an option to export to file from the query window. In the main menu it\'s Query -> Execute to file or there\'s a button that does the same thing (it\'s a green triangle with a blue floppy disk as opposed to the plain green triangle which just runs the query). If you\'re not running the query from the query window then I\'d do what IMSoP suggested and use the copy command.

回答9:

I\'m working on AWS Redshift, which does not support the COPY TO feature.

My BI tool supports tab-delimited CSVs though, so I used the following:

 psql -h  dblocation  -p port -U user  -d dbname  -F $\'\\t\' --no-align -c \" SELECT *   FROM TABLE\" > outfile.csv

回答10:

I\'ve written a little tool called psql2csv that encapsulates the COPY query TO STDOUT pattern, resulting in proper CSV. It\'s interface is similar to psql.

psql2csv [OPTIONS] < QUERY
psql2csv [OPTIONS] QUERY

The query is assumed to be the contents of STDIN, if present, or the last argument. All other arguments are forwarded to psql except for these:

-h, --help           show help, then exit
--encoding=ENCODING  use a different encoding than UTF8 (Excel likes LATIN1)
--no-header          do not output a header

回答11:

If you have longer query and you like to use psql then put your query to a file and use the following command:

psql -d my_db_name -t -A -F\";\" -f input-file.sql -o output-file.csv

回答12:

I tried several things but few of them were able to give me the desired CSV with header details.

Here is what worked for me.

psql -d dbame -U username \\
  -c \"COPY ( SELECT * FROM TABLE ) TO STDOUT WITH CSV HEADER \" > \\
  OUTPUT_CSV_FILE.csv

回答13:

New version - psql 12 - will support --csv.

psql - devel

--csv

Switches to CSV (Comma-Separated Values) output mode. This is equivalent to \\pset format csv.

---

csv_fieldsep

Specifies the field separator to be used in CSV output format. If the separator character appears in a field\'s value, that field is output within double quotes, following standard CSV rules. The default is a comma.

Usage:

psql -c \"SELECT * FROM pg_catalog.pg_tables\" --csv  postgres

psql -c \"SELECT * FROM pg_catalog.pg_tables\" --csv -P csv_fieldsep=\'^\'  postgres

psql -c \"SELECT * FROM pg_catalog.pg_tables\" --csv  postgres > output.csv

回答14:

JackDB, a database client in your web browser, makes this really easy. Especially if you\'re on Heroku.

It lets you connect to remote databases and run SQL queries on them.

                                                                                                                                                       ^Source jackdb-heroku http://static.jackdb.com/assets/img/blog/jackdb-heroku-oauth-connect.gif

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Once your DB is connected, you can run a query and export to CSV or TXT (see bottom right).

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^{Note: I\'m in no way affiliated with JackDB. I currently use their free services and think it\'s a great product.}

回答15:

To Download CSV file with column names as HEADER use this command:

Copy (Select * From tableName) To \'/tmp/fileName.csv\' With CSV HEADER;

回答16:

import json
cursor = conn.cursor()
qry = \"\"\" SELECT details FROM test_csvfile \"\"\" 
cursor.execute(qry)
rows = cursor.fetchall()

value = json.dumps(rows)

with open(\"/home/asha/Desktop/Income_output.json\",\"w+\") as f:
    f.write(value)
print \'Saved to File Successfully\'