Learn more about Database Toolbox

Replacing Existing Data in Databases with Data Exported from the MATLAB Workspace

This example updates the date field that you previously imported into the Avg_Freight_Cost table using the following Database Toolbox functions:

• close

• update

For more information on these functions, see matlab\toolbox\database\dbdemos\dbupdatedemo.m.

1. If you have completed the previous example, skip this step. Otherwise, enter the following commands:

   conn = database('SampleDB', '', '');
   colnames = {'Calc_Date', 'Avg_Cost'};
   D = '20-Jan-2002';
   meanA = 36.6067;
   exdata = {D, meanA}
   exdata = 
   	'20-Jan-2002'    [36.6067]
   

2. Change the date in the Avg_Freight_Cost table from 20-Jan-2002 to 19-Jan-2002:

   D = '19-Jan-2002'
   

3. Assign the new date value to the newdata cell array.

   newdata(1,1) = {D}
   newdata =
       '19-Jan-2002'
   

4. Specify the record to update in the database by defining a SQL where statement and assigning it to the variable whereclause. The record to update is the record whose Calc_Date is 20-Jan-2002. Because the date string is within a string, it is embedded within two single quotation marks rather than one.

   whereclause = 'where Calc_Date = ''20-Jan-2002'''
   whereclause =
   	where Calc_Date = '20-Jan-2002'
   

5. Export the data, replacing the record whose Calc_Date is 20-Jan-2002.

   update(conn,'Avg_Freight_Cost',colnames,newdata,whereclause)

6. In Microsoft Access, view the Avg_Freight_Cost table to verify the results.

   

7. Close the cursor and disconnect from the database.

   close(conn)
   

Exporting Data from the MATLAB Workspace to a New Record in a Database

Exporting Multiple Records from the MATLAB Workspace

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