The issue that you are facing is caused due to removal of JDBC-ODBC bridge connector starting MATLAB R2017a. If you are creating a database connection using the following syntax, it uses the JDBC-ODBC connector (in R2016b and earlier versions):
>> conn = database(instance,username,password)
However, starting MATLAB R2017a, the database connection that is created uses Native ODBC driver (Native ODBC driver is used if "database.ODBC" command is used, for R2016b and earlier versions) and the error that is occurring is being thrown by the Access ODBC driver when a VARCHAR column is created without specifying length
We have two workarounds for the issue:
1. Alter the table and specify the lengths for the columns that are of VARCHAR type.
For instance, if you have a table (Table1) that is having a column called Age which is of VARCHAR type originally, you can specify the length using the following command:
>> exec(conn,'ALTER TABLE Table1 Alter Column Age varchar(30)')
After altering the table the update command should work correctly.
2. Use the "exec" function with a SQL query string.
>> query = 'update MyTable SET Value = 10 where ID = 2';
>> exec(conn, query);
(Note: this is from your active support case, continue working with your TS representative.)