Connection to a database

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Fragkiskos Nikolakis 2017-1-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/320144-connection-to-a-database

编辑： the cyclist 2017-1-12

I have a script in which data from an ORACLE database are called. The problem is that the connection isn't always succesfull. After 3-4 attempts the connection is succesfull. Do you know why does ths happen? Thanks

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the cyclist 2017-1-12

Are you certain that it is not something outside of MATLAB that is failing? It would be unusual for the code itself to be a source of intermittent failure.

Fragkiskos Nikolakis 2017-1-12

编辑：the cyclist 2017-1-12

在 MATLAB Online 中打开

the query for the database is

function[Vessel_Data]=stpQuery(selected_fields1)
% Set preferences with setdbprefs.
s.DataReturnFormat = 'dataset';
s.ErrorHandling = 'store';
s.NullNumberRead = 'NaN';
s.NullNumberWrite = 'NaN';
s.NullStringRead = 'null';
s.NullStringWrite = 'null';
s.JDBCDataSourceFile = '';
s.UseRegistryForSources = 'yes';
s.TempDirForRegistryOutput =  'Path';
s.DefaultRowPreFetch = '10000';
setdbprefs(s)
% Make connection to database.  Note that the password has been omitted.
% Using ODBC driver.
conn = database('Base','usr','pswd');
% Read data from database.
e = exec(conn,selected_fields1);
e = fetch(e);
close(e)
% Assign data to output variable.
Vessel_Data = e.Data;
% Close database connection.
close(conn)