Connect to postgresql database via MATLAB error

Question

I am trying to connect my Postgres database in MATLAB and it is throwing me an error stating

"'JDBC Driver Error: org.postgresql.Driver. Driver Not Found/Loaded.'"

Here's my connection method that i have used.

conn = database('postgres','username','password','org.postgresql.Driver', 'jdbc:postgresql://localhost:5432/postgres=postgres');

after that it throws me the error.

I have looked at forums and they told me to add the postgres jar files to the MATLAB directory toolkit textfile, such as below.

C:\Program Files\PostgreSQL\pgJDBC\postgresql-8.4.702.jdbc3.jar 
C:\Program Files\PostgreSQL\pgJDBC\postgresql-8.4.702.jdbc4.jar

I don't know where else I am going wrong. Please advise.

Thank you.

yuk · Accepted Answer · 2012-01-13 19:29:28Z

2

You should add jar file with JDBC driver to your dynamic java class path before connecting to database. I believe you can add only one file depending on your requirements. Check the versions difference here.

To avoid warning if a jar file already in the path add some check:

%# add class path (if not in the class path)
p = 'C:\Program Files\PostgreSQL\pgJDBC\postgresql-8.4.702.jdbc3.jar';
if ~ismember(p,javaclasspath)
    javaaddpath(p)
end

edited Jan 13, 2012 at 19:29

answered Jan 13, 2012 at 19:14

yuk

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7 Comments

Jeiman Over a year ago

It works. But somehow i can't seem to query an information from the database into MATLAB. Here's the code that i am trying to use : e = exec(conn,'SELECT *FROM cath_2'); e = fetch(e);. This is the error, ??? Undefined function or method 'fetch' for input arguments of type 'struct'.

yuk Over a year ago

How about if you use another variable to return fetch result? rs = fetch(e); I usually just do rs = fetch(exec(conn, qry));. If it does not work try to use another JDBC driver.

yuk Over a year ago

exec actually returns a cursor object, not a structure. Are you using the Database Toolbox?

Jeiman Over a year ago

My apologies, i wrote the url connection wrong. It's fixed now. I got another problem if you dont mind helping me. I am trying to query a table into MATLAB such as this, rs = fetch(exec(conn, 'SELECT * FROM cath_2'));, and it somehow doesnt recognise the table in the database eventhough it does exists. It states 'Invalid Cursor: ERROR: relation "cath_2" does not exist.

yuk Over a year ago

Try query 'show tables'. It should return list of tables in your database. Maybe you connected to a wrong database?

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