Querydb
Purpose
Executes a query on a database defined by connection string.
Synopsis
- out = querydb(connstr,sqlstr,options);
Description
NOTE: As of version 6 of PLS_Toolbox the evridb object should be used in place of this function. See this page for an example of connecting to an Access database.
This function is unsupported and is meant as a "simple" database connection tool. For more sophisticated connection tools and full support please see the Matlab Database Toolbox.
JDBC connections require that the jdbc driver ".jar" file be added to the Matlab java classpath. See the documentation for the Matlab commands 'javaaddpath' and 'javaclasspath' for more information. For example, using the MySQL Connector/J 3.1 driver you'll need to add the "mysql-connector-java-3.1.12-bin.jar" file to your java class path. Check extensions/javatools folder for available connection drivers.
NOTE for using JDBC with Older versions of Matlab:
- The .jar file may need to be added to the Matlab static class path. To do this, add the file path to classpath.txt then restart Matlab.
- The option 'conntype' must be set to jdbc.
Inputs
- connstr : A connection string or a structure created using builddbstr. See BUILDDBSTR for more information.
- sqlstr : A SQL statement to be executed on the connection. The SQL statement must be of proper syntax or it will fail. Default behavior is geared toward SELECT statements that return values. If attempting to execute a SQL command that doesn't return a value (e.g., CREATE TABLE) set the 'rtype' option to 'none'.
NOTE: Use a separate program like Microsoft Access to formulate the SQL statement visually. Access queries can require some small changes in syntax.
Outputs
- out : DataSet Object, Cell Array, or Scalar depending on 'rtype'.
Options
- rtype : [{'dso'} | 'cell' | 'insert' | 'none'] Return type, default is return SQL recordset as a DataSet Object using parsemixed.m to parse data in. If 'cell' then a cell array is returned with all values. If 'insert' then function will execute an "INSERT" type query and attempt to return the Auto Number ID (as a scalar) of the row created. If 'none' function will execute query and return an empty.
- varlabels : [ {'none'} | 'fieldnames' ] Defines what should be used as variable labels on output DataSet Object (only used when rtype is 'dso'). 'fieldnames' uses the SQL field names for variable labels.
- conntype : [ 'jdbc' | {'odbc'} ] Determines type of connection. ODBC uses a Windows ADO with Matlab (descibed above). JDBC connections only work when jdbc class files are on static java path.
- getaccesstables : [ 'on' | {'off'} ] Short circuit to retrieve list of tables in Access database, similar to SHOW TABLES query in MySQL. Input 'sqlstr' will not be called when option is 'on'.
- getaccessfieldnames : [] Short circuit to retrieve list of tables fieldnames. Input should be valid table name (string).
Examples
Assuming there is a connection string named 'mydbconn' already created using the builddbstr command. To return a DSO:
>> sqlstr = 'SELECT * FROM myTable'; >> mydso = querydb(mydbconn,sqlstr);
To return a cell array:
>> opts = querydb('options');
>> opts.rtype = 'cell';
>> mycell = querydb(mydbconn,sqlstr,opts);