I don't know why am getting this error: Undefined function 'fetch' for input arguments of type 'struct'.

The fetch command is well represented in matlab, but I don't know why it is difficult to use. Please I have being on this for a while, any assistance will be appreciated. Many thanks!

------------some code that produce error--------------------

conn = database(file_path, '', '', 'org.sqlite.JDBC', 'jdbc:sqlite:FS_NYC_data.db');
sqlquery = 'select * from dataset_TOKYO';
e=exec(conn,sqlquery); %,'cursorType','scrollable')
setdbprefs('DataReturnFormat','dataset')
curs = curs.fetch(e,50);

Answer 1

[Guillaume]

I think the problem is that you've not fully understood what you are doing. Where does the curs variable come from in your example?

Note that in

e=exec(conn,sqlquery);

the e is a cursor. Obviously the later curs is another cursor (from another query).

Also note, that in matlab,

obj.function(xx, yy)

is the same as

function(obj, xx, yy)

so, your line

curs = curs.fetch(e,50);

is equivalent to

fetch(curs, e, 50)

you're passing two cursors to fetch, which doesn't know what to do with your second cursors. Hence the error (I think, I don't have the db toolbox).

Maybe you meant:

curs = e.fetch(50)

to import up to 50 rows.

[VicPeters]

Thanks Guillaume, I don't really think that is the problem. Using the code as you said still give the same error: Undefined function 'fetch' for input arguments of type 'struct'. I have tried using JDBC data source, still the same error; and now I switched over to ODBC data source the same problem persist. I just want to know if there is any other function apart from 'fetch' that I can use to import the data into matlab. I really help. Below is all my code:

file_path='C:/Users/User/FS_NYC_data.db';
conn = database(file_path, '', '','org.sqlite.JDBC', 'jdbc:sqlite:FS_NYC_data.db');
sqlquery = 'select * from dataset_TOKYO';
curs=exec(conn,sqlquery); %,'cursorType','scrollable')
setdbprefs('DataReturnFormat','dataset')
fetch(curs,e,50);

% Assign data to output variable.
TOKYO_data = curs.Data;
close(conn);

[Guillaume]

What is e in the code you've just posted. If it's a cursor, again, you're passing two cursors to fetch which is not going to work. It should be either:

fetch(curs, 50);  %function notation

or

curs.fetch(50);  %object notation

Also, what is the output of

whos curs e