Database Toolbox cannot store vectors or strings

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James Johnson
James Johnson 2018-2-1
I'm trying to store and retrieve data in an SQLite database with Matlab's Database toolbox. When I try to store strings or vectors as directed by the documentation and then retrieve them I get NaN instead. Additionally, the data should come back as a table but instead, it comes back as a numeric matrix (which may explain the NaN?).
Here is the code:
% create a database from scratch (this is the only documented method I could find)
dbfile=fullfile('test_database.db');
conn=sqlite(dbfile,'create');
close(conn); % this type of interface can be useful but cannot handle null data
% and is not very feature rich
% now we connect to and populate the actual database
% (requires installing a driver first)
conn=database('SQLite','','','org.sqlite.JDBC',['jdbc:sqlite:',dbfile]);
% allow foreign keys so one table can link to other tables
curs=exec(conn,'PRAGMA foreign_keys=ON');
% create a table to store things
create_test_table=['create table test_table (testID NUMERIC PRIMARY KEY,',...
' test_string VARCHAR, test_vector NUMERIC, test_scalar NUMERIC)'];
curs=exec(conn,create_test_table);
% create a new record
datainsert(conn,'test_table','testID',1)
% add data to that record
where_clause=['WHERE testID = ',num2str(1)];
update(conn,'test_table','test_string',{'string1'},where_clause)
update(conn,'test_table','test_vector',{[1,2,3,4]},where_clause)
update(conn,'test_table','test_scalar',1,where_clause)
% now view the data
sqlquery='SELECT * FROM test_table';
data_to_view=fetch(conn,sqlquery)
% same thing happens with this command
% % curs=exec(conn,sqlquery)
% % curs=fetch(curs)
% % curs.Data
ACTUAL RESULT:
data_to_view =
1 NaN NaN 1
EXPECTED RESULT (given the documentation https://www.mathworks.com/help/database/ug/fetch.html):
data_to_view =
1×4 table
testID test_string test_vector test_scalar
_____________ ___________ ______________ ________
1 'string1' 1x4 double 1
The following also returns NaN:
sqlquery='SELECT test_string FROM test_table';
data_to_view=fetch(conn,sqlquery)

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