SQL connection: String that read as several cell array

I want to get hourly data from 15-minute data with sqlquery,

    connection = database ('databasename', 'username', 'password', 'com.mysql.jdbc.Driver', 'jdbc:mysql:address');
    string=['SELECT Hour(inserted_at) AS hour, SUM(duration_consumption) AS SUM_DUR FROM ami_histories WHERE inserted_at >= '' ',date1,' '' AND inserted_at < '' ',date2,' '' AND `cluster`= ',num2str(ami),' GROUP  BY hour'];
    inserted_at >= ' 2017-10-1 00:00:00 ' AND inserted_at < ' 2017-10-02 00:00:00 ' AND `cluster`= 1 GROUP BY hour']
    curs = exec(connection,sqlquery);
    row = fetch (curs);
    raw_data = row.Data;
    dur_consumption = cell2mat(raw_data);

the sqlquery's string should return as sqlquery =

    'SELECT Hour(inserted_at) AS hour, SUM(duration_consumption) AS SUM_DUR FROM ami_histories WHERE inserted_at >= '  2017-10-1 00:00:00  ' AND inserted_at < '  2017-10-02 00:00:00  ' AND `cluster`=  1  GROUP  BY hour'

I have tried that code directly in mysql database, and it is working.

But then, it is read as 1x7 cell array string =

1×7 cell array

    'SELECT Hour(inserted_at)…'    '2017-10-1 00:00:00'    ' ' AND inserted_at < ' '    '2017-10-02 00:00:00'    ' ' AND `cluster`= '    '1'    ' GROUP  BY hour'

To make it as single string, So I put sqlquery=join(string)

Even after I already put single string as sqlquery, the connection doesnt result data that I want, It returns to an error

row =

cursor with properties:

        Attributes: []
              Data: 0
    DatabaseObject: []
          RowLimit: 0
          SQLQuery: []
           Message: 'Invalid Cursor: Second argument must be either a SQL query or object of type sqlOutput'
              Type: 'Database Cursor Object'
         ResultSet: 0
            Cursor: 0
         Statement: 0
             Fetch: 0

raw_data =

     0

Cell contents reference from a non-cell array object.

Error in cell2mat (line 36)
    if isnumeric(c{1}) || ischar(c{1}) || islogical(c{1}) || isstruct(c{1})

Error in hourlyAMI (line 29)
    dur_consumption = cell2mat(raw_data)

What did I do wrong?