sqlread

Import data into MATLAB from database table

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Syntax

data = sqlread(conn,tablename)

data = sqlread(conn,tablename,opts)

data = sqlread(___,Name,Value)

[data,metadata] = sqlread(___)

Description

example

data = sqlread(conn,tablename) returns a table by importing data into MATLAB^® from a database table. Executing this function is the equivalent of writing a SELECT * FROM tablename SQL statement in ANSI SQL.

example

data = sqlread(conn,tablename,opts) customizes options for importing data from a database table using the SQLImportOptions object.

example

data = sqlread(___,Name,Value) specifies additional options using one or more name-value pair arguments and any of the previous input argument combinations. For example, 'Catalog','cat' imports data from a database table stored in the 'cat' catalog.

example

[data,metadata] = sqlread(___) also returns the metadata table, which contains metadata information about the imported data.

Examples

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Import Data from Database Table

Open Script

Use an ODBC connection to import product data from a database table into MATLAB® using a Microsoft® SQL Server® database. Then, perform a simple data analysis.

Create an ODBC database connection to a Microsoft SQL Server database with Windows® authentication. Specify a blank user name and password. The database contains the table productTable.

datasource = 'MS SQL Server Auth';
conn = database(datasource,'','');

Check the database connection. If the Message property is empty, then the connection is successful.

conn.Message

ans =

     []

Import data from the database table productTable. The sqlread function returns a MATLAB® table that contains the product data.

tablename = 'productTable';
data = sqlread(conn,tablename);

Display the first few products.

head(data,3)

ans =

  3×5 table

    productNumber    stockNumber    supplierNumber    unitCost    productDescription
    _____________    ___________    ______________    ________    __________________

          9          1.2597e+05          1003            13        'Victorian Doll' 
          8          2.1257e+05          1001             5        'Train Set'      
          7          3.8912e+05          1007            16        'Engine Kit'

Close the database connection.

close(conn)

Import Data from Database Table Using Import Options

Open Live Script

Customize import options when importing data from a database table. Control the import options by creating an SQLImportOptions object. Then, customize import options for different database columns. Import data using the sqlread function.

This example uses the patients.xls file, which contains the columns Gender, Location, SelfAssessedHealthStatus, and Smoker. The example also uses a Microsoft® SQL Server® Version 11.00.2100 database and the Microsoft SQL Server Driver 11.00.5058.

Create a database connection to a Microsoft SQL Server database with Windows® authentication. Specify a blank user name and password.

datasource = 'MS SQL Server Auth';
conn = database(datasource,'','');

Load patient information into the MATLAB® workspace.

patients = readtable('patients.xls');

Create the patients database table using the patient information.

tablename = 'patients';
sqlwrite(conn,tablename,patients)

Create an SQLImportOptions object using the patients database table and the databaseImportOptions function.

opts = databaseImportOptions(conn,tablename)

opts = 
  SQLImportOptions with properties:

           ExcludeDuplicates: false
          VariableNamingRule: 'modify'

               VariableNames: {'LastName', 'Gender', 'Age' ... and 7 more}
               VariableTypes: {'char', 'char', 'double' ... and 7 more}
       SelectedVariableNames: {'LastName', 'Gender', 'Age' ... and 7 more}
                  FillValues: {'', '',  NaN  ... and 7 more }

             VariableOptions: Show all 10 VariableOptions

Display the current import options for the variables selected in the SelectedVariableNames property of the SQLImportOptions object.

vars = opts.SelectedVariableNames;
varOpts = getoptions(opts,vars)

varOpts = 
    1x10 SQLVariableImportOptions array with properties:

   Variable Options:
                      (1) |      (2) |      (3) |        (4) |      (5) |      (6) |      (7) |        (8) |         (9) |                       (10)
         Name: 'LastName' | 'Gender' |    'Age' | 'Location' | 'Height' | 'Weight' | 'Smoker' | 'Systolic' | 'Diastolic' | 'SelfAssessedHealthStatus'
         Type:     'char' |   'char' | 'double' |     'char' | 'double' | 'double' | 'double' |   'double' |    'double' |                     'char'
  MissingRule:     'fill' |   'fill' |   'fill' |     'fill' |   'fill' |   'fill' |   'fill' |     'fill' |      'fill' |                     'fill'
    FillValue:         '' |       '' |      NaN |         '' |      NaN |      NaN |      NaN |        NaN |         NaN |                         ''

	To access sub-properties of each variable, use getoptions

Change the data types for the Gender, Location, SelfAssessedHealthStatus, and Smoker variables using the setoptions function. Because the Gender, Location, and SelfAssessedHealthStatus variables indicate a finite set of repeating values, change their data type to categorical. Because the Smoker variable stores the values 0 and 1, change its data type to logical. Then, display the updated import options.

opts = setoptions(opts,{'Gender','Location','SelfAssessedHealthStatus'}, ...
    'Type','categorical');
opts = setoptions(opts,'Smoker','Type','logical');

varOpts = getoptions(opts,{'Gender','Location','Smoker', ...
    'SelfAssessedHealthStatus'})

varOpts = 
    1x4 SQLVariableImportOptions array with properties:

   Variable Options:
                         (1) |           (2) |       (3) |                        (4)
         Name:      'Gender' |    'Location' |  'Smoker' | 'SelfAssessedHealthStatus'
         Type: 'categorical' | 'categorical' | 'logical' |              'categorical'
  MissingRule:        'fill' |        'fill' |    'fill' |                     'fill'
    FillValue:   <undefined> |   <undefined> |         0 |                <undefined>

	To access sub-properties of each variable, use getoptions

Import the patients database table using the sqlread function, and display the last eight rows of the table.

data = sqlread(conn,tablename,opts);
tail(data)

ans=8×10 table
      LastName       Gender    Age            Location             Height    Weight    Smoker    Systolic    Diastolic    SelfAssessedHealthStatus
    _____________    ______    ___    _________________________    ______    ______    ______    ________    _________    ________________________

    {'Foster'   }    Female    30     St. Mary's Medical Center      70       124      false       130          91               Fair             
    {'Gonzales' }    Male      48     County General Hospital        71       174      false       123          79               Good             
    {'Bryant'   }    Female    48     County General Hospital        66       134      false       129          73               Excellent        
    {'Alexander'}    Male      25     County General Hospital        69       171      true        128          99               Good             
    {'Russell'  }    Male      44     VA Hospital                    69       188      true        124          92               Good             
    {'Griffin'  }    Male      49     County General Hospital        70       186      false       119          74               Fair             
    {'Diaz'     }    Male      45     County General Hospital        68       172      true        136          93               Good             
    {'Hayes'    }    Male      48     County General Hospital        66       177      false       114          86               Fair

Display a summary of the imported data. The sqlread function applies the import options to the variables in the imported data.

summary(data)

Variables:

    LastName: 100×1 cell array of character vectors

    Gender: 100×1 categorical

        Values:

            Female       53   
            Male         47   

    Age: 100×1 double

        Values:

            Min          25   
            Median       39   
            Max          50   

    Location: 100×1 categorical

        Values:

            County General Hospital         39   
            St. Mary s Medical Center       24   
            VA Hospital                     37   

    Height: 100×1 double

        Values:

            Min          60   
            Median       67   
            Max          72   

    Weight: 100×1 double

        Values:

            Min          111  
            Median     142.5  
            Max          202  

    Smoker: 100×1 logical

        Values:

            True        34   
            False       66   

    Systolic: 100×1 double

        Values:

            Min         109   
            Median      122   
            Max         138   

    Diastolic: 100×1 double

        Values:

            Min           68  
            Median      81.5  
            Max           99  

    SelfAssessedHealthStatus: 100×1 categorical

        Values:

            Excellent       34   
            Fair            15   
            Good            40   
            Poor            11

Delete the patients database table using the execute function.

sqlquery = ['DROP TABLE ' tablename];
execute(conn,sqlquery)

Close the database connection.

close(conn)

Import Data from Database Table in Specific Schema

Open Script

Use an ODBC connection to import product data from a database table into MATLAB® using a Microsoft® SQL Server® database. Specify the schema where the database table is stored. Then, sort and filter the rows in the imported data and perform a simple data analysis.

Create an ODBC database connection to a Microsoft SQL Server database with Windows® authentication. Specify a blank user name and password. The database contains the table productTable.

datasource = 'MS SQL Server Auth';
conn = database(datasource,'','');

Check the database connection. If the Message property is empty, then the connection is successful.

conn.Message

ans =

     []

Import data from the table productTable. Specify the database schema dbo. The data table contains the product data.

tablename = 'productTable';
data = sqlread(conn,tablename,'Schema','dbo');

Display the first few products.

data(1:3,:)

ans =

  3×5 table

    productNumber    stockNumber    supplierNumber    unitCost    productDescription
    _____________    ___________    ______________    ________    __________________

          9          1.2597e+05          1003            13        'Victorian Doll' 
          8          2.1257e+05          1001             5        'Train Set'      
          7          3.8912e+05          1007            16        'Engine Kit'

Display the first few product descriptions.

data.productDescription(1:3)

ans =

  3×1 cell array

    {'Victorian Doll'}
    {'Train Set'     }
    {'Engine Kit'    }

Sort the rows in data by the product description column in alphabetical order.

column = 'productDescription';
data = sortrows(data,column);

Display the first few product descriptions after sorting.

data.productDescription(1:3)

ans =

  3×1 cell array

    {'Building Blocks'}
    {'Convertible'    }
    {'Engine Kit'     }

Close the database connection.

close(conn)

Import Specific Number of Rows from Database Table

Open Script

Use an ODBC connection to import product data from a database table into MATLAB® using a Microsoft® SQL Server® database. Specify the maximum number of rows to import from the database table.

Create an ODBC database connection to a Microsoft SQL Server database with Windows® authentication. Specify a blank user name and password. The database contains the table productTable.

datasource = 'MS SQL Server Auth';
conn = database(datasource,'','');

Check the database connection. If the Message property is empty, then the connection is successful.

conn.Message

ans =

     []

Import data from the table productTable. Import only three rows of data from the database table. The data table contains the product data.

tablename = 'productTable';
data = sqlread(conn,tablename,'MaxRows',3)

data =

  3×5 table

    productNumber    stockNumber    supplierNumber    unitCost    productDescription
    _____________    ___________    ______________    ________    __________________

          9          1.2597e+05          1003            13        'Victorian Doll' 
          8          2.1257e+05          1001             5        'Train Set'      
          7          3.8912e+05          1007            16        'Engine Kit'

Close the database connection.

close(conn)

Preserve Variable Names When Importing Data

Open Live Script

Import product data from a Microsoft® SQL Server® database table into MATLAB® by using an ODBC connection. The table contains a variable name with a non-ASCII character. When importing data, preserve the names of all the variables.

Create an ODBC database connection to an SQL Server database with Windows® authentication. Specify a blank user name and password. The database contains the table productTable.

datasource = "MSSQLServerAuth";
conn = database(datasource,"","");

Check the database connection. If the Message property is empty, then the connection is successful.

conn.Message

ans =

     []

Add a column to the database table productTable. The column name contains a non-ASCII character.

sqlquery = "ALTER TABLE productTable ADD tamaño varchar(30)"; 
execute(conn,sqlquery)

Import data from the database table productTable. The sqlread function returns a MATLAB table that contains the product data. Display the first three rows of the data in the table.

tablename = "productTable";
data = sqlread(conn,tablename);
head(data,3)

ans=3×6 table
    productNumber    stockNumber    supplierNumber    unitCost    productDescription      tama_o  
    _____________    ___________    ______________    ________    __________________    __________

          9          1.2597e+05          1003            13       {'Victorian Doll'}    {0×0 char}
          8          2.1257e+05          1001             5       {'Train Set'     }    {0×0 char}
          7          3.8912e+05          1007            16       {'Engine Kit'    }    {0×0 char}

The sqlread function converts the name of the new variable into ASCII characters.

Preserve the name of the variable that contains the non-ASCII character by specifying the VariableNamingRule name-value pair argument. Import the data again.

data = sqlread(conn,tablename, ...
    'VariableNamingRule',"preserve");
head(data,3)

ans=3×6 table
    productNumber    stockNumber    supplierNumber    unitCost    productDescription      tamaño  
    _____________    ___________    ______________    ________    __________________    __________

          9          1.2597e+05          1003            13       {'Victorian Doll'}    {0×0 char}
          8          2.1257e+05          1001             5       {'Train Set'     }    {0×0 char}
          7          3.8912e+05          1007            16       {'Engine Kit'    }    {0×0 char}

The sqlread function preserves the non-ASCII character in the variable name.

Close the database connection.

close(conn)

Retrieve Metadata Information About Imported Data

Open Live Script

Retrieve metadata information when importing data from a database table. Import data using the sqlread function and explore the metadata information by using dot notation.

This example uses the outages.csv file, which contains outage data. Also, the example uses a Microsoft® SQL Server® Version 11.00.2100 database and the Microsoft SQL Server Driver 11.00.5058.

Create a database connection to a Microsoft SQL Server database with Windows® authentication. Specify a blank user name and password.

datasource = "MS SQL Server Auth";
conn = database(datasource,"","");

Load outage information into the MATLAB® workspace.

outages = readtable("outages.csv");

Create the outages database table using the outage information.

tablename = "outages";
sqlwrite(conn,tablename,outages)

Import the data into the MATLAB workspace and return metadata information about the imported data.

[data,metadata] = sqlread(conn,tablename);

View the names of the variables in the imported data.

metadata.Properties.RowNames

ans = 6×1 cell array
    {'Region'         }
    {'OutageTime'     }
    {'Loss'           }
    {'Customers'      }
    {'RestorationTime'}
    {'Cause'          }

View the data type of each variable in the imported data.

metadata.VariableType

ans = 6×1 cell array
    {'char'  }
    {'char'  }
    {'double'}
    {'double'}
    {'char'  }
    {'char'  }

View the missing data value for each variable in the imported data.

metadata.FillValue

ans = 6×1 cell array
    {0×0 char}
    {0×0 char}
    {[   NaN]}
    {[   NaN]}
    {0×0 char}
    {0×0 char}

View the indices of the missing data for each variable in the imported data.

metadata.MissingRows

ans = 6×1 cell array
    {  0×1 double}
    {  0×1 double}
    {604×1 double}
    {328×1 double}
    { 29×1 double}
    {  0×1 double}

Display the first eight rows of the imported data that contain missing restoration time. data contains restoration time in the fifth variable. Use the numeric indices to find the rows with missing data.

index = metadata.MissingRows{5,1};
nullrestoration = data(index,:);
head(nullrestoration)

ans=8×6 table
      Region              OutageTime             Loss     Customers     RestorationTime          Cause       
    ___________    _________________________    ______    __________    _______________    __________________

    'SouthEast'    '2003-01-23 00:49:00.000'    530.14    2.1204e+05          ''           'winter storm'    
    'NorthEast'    '2004-09-18 05:54:00.000'         0             0          ''           'equipment fault' 
    'MidWest'      '2002-04-20 16:46:00.000'     23141           NaN          ''           'unknown'         
    'NorthEast'    '2004-09-16 19:42:00.000'      4718           NaN          ''           'unknown'         
    'SouthEast'    '2005-09-14 15:45:00.000'    1839.2    3.4144e+05          ''           'severe storm'    
    'SouthEast'    '2004-08-17 17:34:00.000'     624.1    1.7879e+05          ''           'severe storm'    
    'SouthEast'    '2006-01-28 23:13:00.000'    498.78           NaN          ''           'energy emergency'
    'West'         '2003-06-20 18:22:00.000'         0             0          ''           'energy emergency'

Delete the outages database table using the execute function.

sqlstr = "DROP TABLE ";
sqlquery = strcat(sqlstr,tablename);
execute(conn,sqlquery)

Close the database connection.

close(conn)

Input Arguments

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`conn` — Database connection
`connection` object

Database connection, specified as a connection object created with the database function.

`tablename` — Database table name
character vector | string scalar

Database table name, specified as a character vector or string scalar denoting the name of a table in the database.

Example: 'employees'

Data Types: char | string

`opts` — Database import options
`SQLImportOptions` object

Database import options, specified as an SQLImportOptions object.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example:

data =
                    sqlread(conn,'inventoryTable','Catalog','toy_store','Schema','dbo','MaxRows',5)

imports five rows of data from the database table inventoryTable stored in the toy_store catalog and the dbo schema.

`'Catalog'` — Database catalog name
character vector | string scalar

Database catalog name, specified as the comma-separated pair consisting of 'Catalog' and a character vector or string scalar. A catalog serves as the container for the schemas in a database and contains related metadata information. A database can have numerous catalogs.

Example: 'Catalog','toy_store'

Data Types: char | string

`'Schema'` — Database schema name
character vector | string scalar

Database schema name, specified as the comma-separated pair consisting of 'Schema' and a character vector or string scalar. A schema defines the database tables, views, relationships among tables, and other elements. A database catalog can have numerous schemas.

Example: 'Schema','dbo'

Data Types: char | string

`'MaxRows'` — Maximum number of rows to return
positive numeric scalar

Maximum number of rows to return, specified as the comma-separated pair consisting of 'MaxRows' and a positive numeric scalar. By default, the sqlread function returns all rows from the executed SQL query. Use this name-value pair argument to limit the number of rows imported into MATLAB.

Example: 'MaxRows',10

Data Types: double

`'VariableNamingRule'` — Variable naming rule
`"modify"` (default) | `"preserve"`

Variable naming rule, specified as the comma-separated pair consisting of 'VariableNamingRule' and one of these values:

"modify" — Remove non-ASCII characters from variable names when the sqlread function imports data.
"preserve" — Preserve most variable names when the sqlread function imports data. For details, see the Limitations section.

Example: 'VariableNamingRule',"modify"

Data Types: string

Output Arguments

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`data` — Imported data
table

Imported data, returned as a table. The rows of the table correspond to the rows in the database table tablename. The variables in the table correspond to each column in the database table. For columns that have numeric data types in the database table, the variable data types in data are double by default. For columns that have text, date, time, or timestamp data types in the database table, the variable data types are cell arrays of character vectors by default.

If the database table contains no data to import, then data is an empty table.

`metadata` — Metadata information
table

Metadata information, returned as a table with these variables.

Variable Name	Variable Description	Variable Data Type
`VariableType`	Data type of each variable in the imported data	Cell array of character vectors
`FillValue`	Value of missing data for each variable in the imported data	Cell array of missing data values
`MissingRows`	Indices for each occurrence of missing data in each variable of the imported data	Cell array of numeric indices

By default, the sqlread function imports text data as a character vector and numeric data as a double. FillValue is an empty character array (for text data) or NaN (for numeric data) by default. To change the missing data value to another value, use the SQLImportOptions object.

The RowNames property of the metadata table contains the names of the variables in the imported data.

Limitations

The name-value pair argument 'VariableNamingRule' has these limitations:

The sqlread function returns an error when you use the 'VariableNamingRule' name-value pair argument with the SQLImportOptions object opts.
When the 'VariableNamingRule' name-value pair argument is set to the value 'modify':
- The variable names Properties, RowNames, and VariableNames are reserved identifiers for the table data type.
- The length of each variable name must be less than the number returned by namelengthmax.

Documentation

sqlread

Syntax

Description

Examples

Import Data from Database Table

Import Data from Database Table Using Import Options

Import Data from Database Table in Specific Schema

Import Specific Number of Rows from Database Table

Preserve Variable Names When Importing Data

Retrieve Metadata Information About Imported Data

Input Arguments

`conn` — Database connection
`connection` object

`tablename` — Database table name
character vector | string scalar

`opts` — Database import options
`SQLImportOptions` object

Name-Value Pair Arguments

`'Catalog'` — Database catalog name
character vector | string scalar

`'Schema'` — Database schema name
character vector | string scalar

`'MaxRows'` — Maximum number of rows to return
positive numeric scalar

`'VariableNamingRule'` — Variable naming rule
`"modify"` (default) | `"preserve"`

Output Arguments

`data` — Imported data
table

`metadata` — Metadata information
table

Limitations

See Also

Topics

Database Toolbox Documentation

Support

Documentation

sqlread

Syntax

Description

Examples

Import Data from Database Table

Import Data from Database Table Using Import Options

Import Data from Database Table in Specific Schema

Import Specific Number of Rows from Database Table

Preserve Variable Names When Importing Data

Retrieve Metadata Information About Imported Data

Input Arguments

conn — Database connection connection object

tablename — Database table name character vector | string scalar

opts — Database import options SQLImportOptions object

Name-Value Pair Arguments

'Catalog' — Database catalog name character vector | string scalar

'Schema' — Database schema name character vector | string scalar

'MaxRows' — Maximum number of rows to return positive numeric scalar

'VariableNamingRule' — Variable naming rule "modify" (default) | "preserve"

Output Arguments

data — Imported data table

metadata — Metadata information table

Limitations

See Also

Topics

Database Toolbox Documentation

Support

`conn` — Database connection
`connection` object

`tablename` — Database table name
character vector | string scalar

`opts` — Database import options
`SQLImportOptions` object

`'Catalog'` — Database catalog name
character vector | string scalar

`'Schema'` — Database schema name
character vector | string scalar

`'MaxRows'` — Maximum number of rows to return
positive numeric scalar

`'VariableNamingRule'` — Variable naming rule
`"modify"` (default) | `"preserve"`

`data` — Imported data
table

`metadata` — Metadata information
table