Why does fetch command for sql query fail but runsqlscript work?

I am connecting to a PostgresQL compliant database and am unable to use the fetch command. It returns a "Invalid fetch cursor". However, if I run the same query using runsqlscript with a *.sql file, it works.

conn=database('dbname','user','pwd','postgresql-9.4.1207','jdbc:address');
resultsFail=fetch(conn,sqlquery); # Returns 'Invalid fetch cursor'
resultsGood=runsqlscript(conn,'test.sql'); 

# Returns    
date
------------
 2016-01-14

Answer 1

[Bryan Yu]

The answer is that there is a bug in MATLAB 2015b. In order to get this to work use set(conn, 'AutoCommit', 'off').

http://www.mathworks.com/help/database/ug/set.html?refresh=true

[Tushar Athawale]

This bug has been fixed in MATLAB R2016a.

Answer 2

[Tushar Athawale]

Hi Bryan,

The error you are receiving is most likely due to invalid database connection or invalid SQL query. In order to troubleshoot the issue regarding the "fetch" command:

1) What is the value of the 'Message' property of the database connection? In your example, it can be checked using the following command:

>> conn.Message

2) What is the exact SQL query that you are trying to execute?

3) Please try fetching data from the database using alternative workflow as provided on: http://www.mathworks.com/help/database/ug/importing-data-using-the-fetch-function.html. In your example, please execute the following MATLAB commands:

>> curs = exec(conn,sqlquery)
>> curs = fetch(curs)

Can you execute the above commands successfully? If not, what is the exact error message that you are receiving?

[Bryan Yu]

1.

>> conn.Message
ans = 
      []

2. As of now I'm just trying to run a simple query to verify connection.

'select current_date'

3. These commands are executed successfully but the curs object after running:

>> curs = fetch(curs)

cursor with properties:

        Attributes: []
              Data: 0
    DatabaseObject: [1x1 database]
          RowLimit: 0
          SQLQuery: 'select current_date'
           Message: 'Invalid fetch cursor.'
              Type: 'Database Cursor Object'
         ResultSet: 0
            Cursor: 0
         Statement: [1x1 com.amazon.redshift.core.jdbc41.PGJDBC41Statement]
             Fetch: [1x1 com.mathworks.toolbox.database.fetchTheData]