hasdata

Determine if data in DatabaseDatastore is available to read

Syntax

tf = hasdata(dbds)

Description

example

tf = hasdata(dbds) returns logical 1 (true) if there is data available to read from the DatabaseDatastore object dbds. Otherwise, it returns logical 0 (false).

Examples

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Create a database connection using a JDBC driver. To create this connection, you must configure a JDBC data source. For more information, see the configureJDBCDataSource function. Then, create a DatabaseDatastore object and read the data stored in the object until no more data remains.

Create a database connection to the JDBC data source MSSQLServerJDBCAuth. This data source configures a JDBC driver to a Microsoft® SQL Server® database with Windows® authentication. Specify a blank user name and password.

datasource = "MSSQLServerJDBCAuth";
username = "";
password = "";
conn = database(datasource,username,password);

Create a DatabaseDatastore object using the database connection and an SQL query. This SQL query reads the first 30 rows of data from the airlinesmall table.

sqlquery = 'select top 30 * from airlinesmall';

dbds = databaseDatastore(conn,sqlquery);

Read the first 10 rows.

dbds.ReadSize = 10;
read(dbds)
ans =

  10×29 table

    Year    Month    DayofMonth    DayOfWeek    DepTime    CRSDepTime    ArrTime    CRSArrTime    UniqueCarrier    FlightNum    TailNum    ActualElapsedTime    CRSElapsedTime    AirTime    ArrDelay    DepDelay    Origin    Dest     Distance    TaxiIn    TaxiOut    Cancelled    CancellationCode    Diverted    CarrierDelay    WeatherDelay    NASDelay    SecurityDelay    LateAircraftDelay
    ____    _____    __________    _________    _______    __________    _______    __________    _____________    _________    _______    _________________    ______________    _______    ________    ________    ______    _____    ________    ______    _______    _________    ________________    ________    ____________    ____________    ________    _____________    _________________

    1987     10          30            5         1329         1329        1434         1436           'US'            683        'NA'              65                 67           'NA'         -2           0       'LGA'     'BUF'       292       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1987     11           7            6         1316         1315        1713         1647           'TW'            810        'NA'             177                152           'NA'         26           1       'STL'     'BOS'      1046       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1987     11          28            6          815          815        1015         1015           'WN'            441        'NA'             120                120           'NA'          0           0       'BNA'     'HOU'       670       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1987     11           2            1          700          700         800          800           'NW'            790        'NA'              60                 60           'NA'          0           0       'BTR'     'MEM'       319       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1987     11          14            6          840          840        1127         1120           'CO'            733        'NA'             167                160           'NA'          7           0       'EWR'     'MCO'       938       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1987     11           1            7         1625         1625        1823         1758           'DL'            957        'NA'             118                 93           'NA'         25           0       'EWR'     'CVG'       569       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1987     11          26            4         1314         1315        1538         1542           'AA'            398        'NA'              84                 87           'NA'         -4          -1       'BNA'     'RDU'       443       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1990     10          12            5         1755         1733        1858         1820           'DL'            590        'NA'              63                 47           'NA'         38          22       'BOS'     'BGR'       201       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1990     10          19            5         1130         1120        1203         1154           'UA'            369        'NA'              93                 94           'NA'          9          10       'BUF'     'ORD'       473       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1990     10           8            1         1515         1440        1609         1535           'NW'            749        'NA'              54                 55           'NA'         34          35       'MSP'     'FSD'       197       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       

Determine if the DatabaseDatastore object has additional data.

hasdata(dbds)
ans =

  logical

   1

When more data is available in dbds, hasdata returns 1.

Read the rest of the data in dbds, 10 rows at a time.

while(hasdata(dbds))
     read(dbds)
end
ans =

  10×29 table

    Year    Month    DayofMonth    DayOfWeek    DepTime    CRSDepTime    ArrTime    CRSArrTime    UniqueCarrier    FlightNum    TailNum     ActualElapsedTime    CRSElapsedTime    AirTime    ArrDelay    DepDelay    Origin    Dest     Distance    TaxiIn    TaxiOut    Cancelled    CancellationCode    Diverted    CarrierDelay    WeatherDelay    NASDelay    SecurityDelay    LateAircraftDelay
    ____    _____    __________    _________    _______    __________    _______    __________    _____________    _________    ________    _________________    ______________    _______    ________    ________    ______    _____    ________    ______    _______    _________    ________________    ________    ____________    ____________    ________    _____________    _________________

    1990     10          23            2         1057         1055        1205         1155           'US'           1621       'NA'                68                 60           'NA'         10           2       'ROC'     'EWR'       246       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1990     10          27            6         1353         1355        1634         1640           'US'            112       'NA'               161                165           'NA'         -6          -2       'TPA'     'SYR'      1104       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1990      9          11            2         1810         1812        1939         1930           'AA'           1426       'NA'                89                 78           'NA'          9          -2       'RST'     'ORD'       268       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1992      7          18            6         1538         1540        1703         1720           'NW'            199       'NA'               145                160           'NA'        -17          -2       'DCA'     'MSP'       931       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1992      7          19            7          932          932        1130         1052           'AA'           1433       'NA'               118                 80           'NA'         38           0       'DFW'     'HRL'       461       'NA'      'NA'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    1992      8           4            2          NaN         1815         NaN         1940           'US'            127       'NA'               NaN                 85           'NA'        NaN         NaN       'EWR'     'PIT'       319       'NA'      'NA'          1              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2001     12           9            7          656          650         824          823           'DL'           1224       'N37438'            88                 93           '73'          1           6       'ATL'     'BWI'       576       '4'       '11'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2001     12          22            6         1707         1715        1823         1821           'UA'            725       'N361ä1'           136                126           '104'         2          -8       'RIC'     'ORD'       642       '20'      '12'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2001     12           8            6         1402         1410        1642         1626           'NW'            809       'N324N2'           220                196           '199'        16          -8       'BOS'     'MEM'      1139       '4'       '17'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2001     12          23            7         1327         1310        1530         1530           'WN'            658       'N789@@'            63                 80           '48'          0          17       'SNA'     'PHX'       338       '5'       '10'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       


ans =

  10×29 table

    Year    Month    DayofMonth    DayOfWeek    DepTime    CRSDepTime    ArrTime    CRSArrTime    UniqueCarrier    FlightNum    TailNum     ActualElapsedTime    CRSElapsedTime    AirTime    ArrDelay    DepDelay    Origin    Dest     Distance    TaxiIn    TaxiOut    Cancelled    CancellationCode    Diverted    CarrierDelay    WeatherDelay    NASDelay    SecurityDelay    LateAircraftDelay
    ____    _____    __________    _________    _______    __________    _______    __________    _____________    _________    ________    _________________    ______________    _______    ________    ________    ______    _____    ________    ______    _______    _________    ________________    ________    ____________    ____________    ________    _____________    _________________

    2001     11          18            7         1407         1415        1442         1457           'DL'            628       'N521D1'            35                 42           '22'        -15          -8       'OKC'     'TUL'       111       '3'       '10'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2001     11          26            1         2105         2110        2209         2237           'AA'           1947       'N3BäA1'            64                 87           '47'        -28          -5       'SFO'     'LAX'       337       '6'       '11'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2001     11          22            4         1345         1355        1530         1549           'MQ'           4982       '#NAME?'           105                114           '90'        -19         -10       'JAX'     'MIA'       334       '8'       '7'           0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2002      7          25            4         1032         1035        1853         1852           'US'            180       'N174UW'           321                317           '289'         1          -3       'SEA'     'PHL'      2378       '9'       '23'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2002      6           5            3         2032         2031        2233         2248           'AA'           3163       'N4WFAA'           241                257           '220'       -15           1       'STL'     'SMF'      1679       '8'       '13'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2002      6          26            3         2026         1840          47         2257           'AA'            636       'N420AA'           141                137           '115'       110         106       'PHX'     'DFW'       868       '6'       '20'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2002      6           8            6         1557         1600        1703         1711           'HP'            660       'N334AW'            66                 71           '52'         -8          -3       'PHX'     'SNA'       338       '4'       '10'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2002      6          15            6         1120         1115        1401         1413           'DL'            406       'N1402A'           161                178           '132'       -12           5       'FLL'     'LGA'      1076       '7'       '22'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2002      6          10            1          927          930        1031         1031           'UA'            501       'N304UA'           124                121           '101'         0          -3       'DFW'     'DEN'       641       '5'       '18'          0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       
    2002      6          19            3          632          640         748          756           'NW'            126       'N773NC'            76                 76           '58'         -8          -8       'BIS'     'MSP'       386       '9'       '9'           0              'NA'             0            'NA'            'NA'          'NA'          'NA'               'NA'       

When no more data remains in dbds, hasdata returns logical 0 and the while loop stops.

Close the DatabaseDatastore object and the database connection.

close(dbds)

Input Arguments

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Datastore containing data in a database, specified as a DatabaseDatastore object created using the databaseDatastore function.

Introduced in R2014b