Why am I getting this error when creating an SQL query in MATLAB?

Question

I'm trying to export some data from MATLAB to a database. I use a PostgreSQL database via ODBC as follows. First, I create the connection:

dbConn = database('PostgreSQL30', username,password);

If I try to execute some test insertion manually, everything looks fine:

exec( dbConn, 'insert into test(std) values(2.2)')

When I try to generate some short query dynamically, everything still looks fine:

q = sprintf('insert into test(std) values(%2.2f)', 12.345);
res = exec(dbConn, q);

But when I try to generate some query containing strings, I get an error:

>> q = sprintf('insert into test(name) values("%s")', 'xxx')

q =

insert into test(name) values("xxx")

>> res = exec(dbConn, q);
>> res.Message
ans =

ERROR: column "xxx" does not exist;
Error while executing the query

There is no difference if I use "%s" format or plain %s. Where is the problem?

EDIT

OK, I used the wrong quotation marks. When I use:

q = sprintf('insert into test(name) values(''%s'')', 'xxx')

everything is OK. So the question can be closed/deleted. Sorry to bother you.

It doesn't necessarily have to be closed. It may help someone else who comes here with the same problem. — gnovice
– gnovice, Commented Dec 21, 2009 at 17:39
on an unrelated note, I once used pgmex library to interface with PostgreSQL from MATLAB (uses the libpq C library directly): dertech.com/pgmex/pgmex.html — Amro
– Amro, Commented Dec 21, 2009 at 18:54
but the built-in functions to communicate matlab with postgres are quite good, is there any significant difference in using pgmex? — Gacek
– Gacek, Commented Dec 21, 2009 at 20:21
the built-ins connect using ODBC, as opposed to using the native C API functions though mex. Therefore its a performance issue since you can think of ODBC as a middleware layer... — Amro
– Amro, Commented Dec 21, 2009 at 21:29
did you add the corresponding JDBC jar file to the javaclasspath? you can get the latest PostgreSQL JDBC driver at jdbc.postgresql.org — Amro
– Amro, Commented Dec 21, 2009 at 23:12

gnovice · Accepted Answer · 2009-12-21 17:33:37Z

4

Have you tried using single quotes?

>> q = sprintf('insert into test(name) values(''%s'')', 'xxx')

q =

insert into test(name) values('xxx')

answered Dec 21, 2009 at 17:33

gnovice

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1 Comment

Gacek Over a year ago

Yup, I came up with the same thing. Thanks for the answer.

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