Database Toolbox™

Saving Queries in M-Files

About Generated M-Files

Select Query > Generate M-File to create an M-file that contains the equivalent Database Toolbox functions required to run an existing query that was created in VQB. Edit the M-file to include MATLAB or related toolbox functions, as needed. To run the query, execute the M-file.

The following is an example of an M-file generated by VQB.

% Set preferences with setdbprefs.
s.DataReturnFormat = 'cellarray';
s.ErrorHandling = 'store';
s.NullNumberRead = 'NaN';
s.NullNumberWrite = 'NaN';
s.NullStringRead = 'null';
s.NullStringWrite = 'null';
s.JDBCDataSourceFile = '';
s.UseRegistryForSources = 'yes';
s.TempDirForRegistryOutput = '';
setdbprefs(s)

% Make connection to database. Note that the password has been omitted.
% Using ODBC driver.
conn = database('dbtoolboxdemo','','password');

% Read data from database.
e = exec(conn,'SELECT ALL StockNumber,January,February FROM salesVolume');
e = fetch(e);
close(e)

% Close database connection.
close(conn)

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VQB Query Elements in M-Files

The following VQB query elements do not appear in generated M-files.

• Generated M-files do not include MATLAB workspace variables to which you assigned query results in the VQB query. The M-file assigns the query results to e; access these results using the variable e.Data. For example, you can add a statement to the M-file that assigns a variable name to e.Data as follows:

  myVar = e.Data

• For security reasons, generated M-files do not include passwords required to connect to databases. Instead, the database statement includes the string 'password' as a placeholder. To run M-files to connect to databases that require passwords, substitute your password for the string password in the database statement.

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Importing and Exporting BOOLEAN Data

Using Database Toolbox Functions