read
Read data in DatabaseDatastore
Description
returns
data from the data
= read(dbds
)DatabaseDatastore
object in increments
specified by the ReadSize
property of the DatabaseDatastore
object.
Subsequent calls to the read
function continue
reading from the endpoint of the previous call.
Note
read
returns data as a table only.
read
ignores database preference settings for
data return formatting.
If there is no more data to read from the query,
read
throws an error.
Examples
Read Data
Create a database connection using a JDBC driver. To create this connection, you must configure a JDBC data source. For more information, see the
function. Then, create a configureJDBCDataSource
DatabaseDatastore
object and read the data stored in the object.
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 retrieves all data from the airlinesmall
table. Specify reading a maximum of 10 records from the executed SQL query.
sqlquery = 'select * from airlinesmall'; dbds = databaseDatastore(conn,sqlquery,'ReadSize',10);
Read the data in the DatabaseDatastore
object.
data = read(dbds)
data = 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' 1987 10 28 3 1140 1140 1212 1215 'US' 262 'NA' 32 35 'NA' -3 0 'CLE' 'PIT' 105 'NA' 'NA' 0 'NA' 0 'NA' 'NA' 'NA' 'NA' 'NA' 1987 10 9 5 1155 1155 1250 1300 'US' 282 'NA' 55 65 'NA' -10 0 'ROC' 'LGA' 254 'NA' 'NA' 0 'NA' 0 'NA' 'NA' 'NA' 'NA' 'NA' 1987 10 22 4 715 715 807 803 'US' 304 'NA' 52 48 'NA' 4 0 'DTW' 'PIT' 201 'NA' 'NA' 0 'NA' 0 'NA' 'NA' 'NA' 'NA' 'NA'
data
contains the query results.
Close the DatabaseDatastore
object and the database connection.
close(dbds)
Read Data and Retrieve Database Information
Create a database connection using a JDBC driver. To create this connection, you must configure a JDBC data source. For more information, see the
function. Then, create a configureJDBCDataSource
DatabaseDatastore
object, read the data stored in the object, and retrieve information about the database.
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 retrieves all data from the airlinesmall
table. Specify reading a maximum of 10 records from the executed SQL query.
sqlquery = 'select * from airlinesmall'; dbds = databaseDatastore(conn,sqlquery,'ReadSize',10);
Read the data in the DatabaseDatastore
object, and retrieve information about the database.
[data,info] = read(dbds)
data = 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' 1987 10 28 3 1140 1140 1212 1215 'US' 262 'NA' 32 35 'NA' -3 0 'CLE' 'PIT' 105 'NA' 'NA' 0 'NA' 0 'NA' 'NA' 'NA' 'NA' 'NA' 1987 10 9 5 1155 1155 1250 1300 'US' 282 'NA' 55 65 'NA' -10 0 'ROC' 'LGA' 254 'NA' 'NA' 0 'NA' 0 'NA' 'NA' 'NA' 'NA' 'NA' 1987 10 22 4 715 715 807 803 'US' 304 'NA' 52 48 'NA' 4 0 'DTW' 'PIT' 201 'NA' 'NA' 0 'NA' 0 'NA' 'NA' 'NA' 'NA' 'NA' info = struct with fields: datasource: 'MSSQLServerJDBCAuth' offset: 10
data
contains the query results. The structure info
contains the data source name datasource
and current cursor position offset
.
Close the DatabaseDatastore
object and the database connection.
close(dbds)
Input Arguments
dbds
— Datastore containing data in database
DatabaseDatastore
object
Datastore containing data in a database, specified as a DatabaseDatastore
object
created using the databaseDatastore
function.
Output Arguments
data
— Query results
table
Query results, returned as a table of the records in the data
set. Executing the SQL statement specified in the Query
property
of the DatabaseDatastore
object creates the data
set. The ReadSize
property of the DatabaseDatastore
object
specifies the number of rows in the table.
If there is no more data to read from the query, read
throws
an error.
info
— Database information
structure
Database information, returned as a structure with these fields.
Field | Description |
---|---|
| Data source name for ODBC drivers or a database name for JDBC drivers |
| Current cursor position in the returned data set |
Version History
Introduced in R2014b
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