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## weka.experiment
Class InstanceQuery

    java.lang.Object
      weka.experiment.DatabaseUtils
          weka.experiment.InstanceQuery

All Implemented Interfaces:
  java.io.Serializable, OptionHandler

    public class InstanceQuery

extends DatabaseUtils
implements OptionHandler

Convert the results of a database query into instances. The jdbc driver and database to be used default to "jdbc.idbDriver" and "jdbc:idb=experiments.prp". These may be changed by creating a java properties file called DatabaseUtils.props in user.home or the current directory. eg:

``

     jdbcDriver=jdbc.idbDriver
     jdbcURL=jdbc:idb=experiments.prp

Command line use just outputs the instances to System.out.

Version:
  $Revision: 1.15.2.1 $
Author:
  Len Trigg (trigg@cs.waikato.ac.nz)
See Also:
  Serialized Form

Field Summary

Fields inherited from class weka.experiment.DatabaseUtils
`BOOL, BYTE, DATE, DOUBLE, EXP_INDEX_TABLE, EXP_RESULT_COL, EXP_RESULT_PREFIX, EXP_SETUP_COL, EXP_TYPE_COL, FLOAT, INTEGER, LONG, PROPERTY_FILE, SHORT, STRING`

Constructor Summary
`InstanceQuery()` Sets up the database drivers

Method Summary
`java.lang.String[]` | `getOptions()` Gets the current settings of InstanceQuery
`java.lang.String` | `getQuery()` Get the query to execute against the database
`boolean` | `getSparseData()` Gets whether data is to be returned as a set of sparse instances
`java.util.Enumeration` | `listOptions()` Returns an enumeration describing the available options
`static void` | `main(java.lang.String[] args)` Test the class from the command line.
`java.lang.String` | `queryTipText()` Returns the tip text for this property
`Instances` | `retrieveInstances()` Makes a database query using the query set through the -Q option to convert a table into a set of instances
`Instances` | `retrieveInstances(java.lang.String query)` Makes a database query to convert a table into a set of instances
`void` | `setOptions(java.lang.String[] options)` Parses a given list of options.
`void` | `setQuery(java.lang.String q)` Set the query to execute against the database
`void` | `setSparseData(boolean s)` Sets whether data should be encoded as sparse instances
`java.lang.String` | `sparseDataTipText()` Returns the tip text for this property

Methods inherited from class weka.experiment.DatabaseUtils
`arrayToString, connectToDatabase, createExperimentIndex, createExperimentIndexEntry, createResultsTable, databaseURLTipText, debugTipText, disconnectFromDatabase, execute, experimentIndexExists, getDatabaseURL, getDebug, getPassword, getResultFromTable, getResultSet, getResultsTableName, getUsername, isConnected, passwordTipText, processKeyString, putResultInTable, setDatabaseURL, setDebug, setPassword, setUsername, tableExists, translateDBColumnType, typeName, usernameTipText`

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### InstanceQuery

    public InstanceQuery()
                  throws java.lang.Exception

  Sets up the database drivers

  Throws:
    `java.lang.Exception` - if an error occurs

Method Detail

### listOptions

    public java.util.Enumeration listOptions()

  Returns an enumeration describing the available options

  Specified by:
    `listOptions` in interface `OptionHandler`
  Returns:
    an enumeration of all available options.

### setOptions

    public void setOptions(java.lang.String[] options)
                    throws java.lang.Exception

  Parses a given list of options. Valid options are:

  -Q query
  The query to execute.

  -S
  Return a set of sparse instances rather than normal instances.

  -U username
  The username to connect with.

  -P password
  The password to connect with.

  Specified by:
    `setOptions` in interface `OptionHandler`
  Parameters:
    `options` - the list of options as an array of strings
  Throws:
    `java.lang.Exception` - if an option is not supported

### queryTipText

    public java.lang.String queryTipText()

  Returns the tip text for this property

  Returns:
    tip text for this property suitable for displaying in the explorer/experimenter gui

### setQuery

    public void setQuery(java.lang.String q)

  Set the query to execute against the database

  Parameters:
    `q` - the query to execute

### getQuery

    public java.lang.String getQuery()

  Get the query to execute against the database

  Returns:
    the query

### sparseDataTipText

    public java.lang.String sparseDataTipText()

  Returns the tip text for this property

  Returns:
    tip text for this property suitable for displaying in the explorer/experimenter gui

### setSparseData

    public void setSparseData(boolean s)

  Sets whether data should be encoded as sparse instances

  Parameters:
    `s` - true if data should be encoded as a set of sparse instances

### getSparseData

    public boolean getSparseData()

  Gets whether data is to be returned as a set of sparse instances

  Returns:
    true if data is to be encoded as sparse instances

### getOptions

    public java.lang.String[] getOptions()

  Gets the current settings of InstanceQuery

  Specified by:
    `getOptions` in interface `OptionHandler`
  Returns:
    an array of strings suitable for passing to setOptions()

### retrieveInstances

    public Instances retrieveInstances()
                                throws java.lang.Exception

  Makes a database query using the query set through the -Q option to convert a table into a set of instances

  Returns:
    the instances contained in the result of the query
  Throws:
    `java.lang.Exception` - if an error occurs

### retrieveInstances

    public Instances retrieveInstances(java.lang.String query)
                                throws java.lang.Exception

  Makes a database query to convert a table into a set of instances

  Parameters:
    `query` - the query to convert to instances
  Returns:
    the instances contained in the result of the query, NULL if the SQL query doesn't return a ResultSet, e.g., DELETE/INSERT/UPDATE
  Throws:
    `java.lang.Exception` - if an error occurs

### main

    public static void main(java.lang.String[] args)

  Test the class from the command line. The instance query should be specified with -Q sql_query

  Parameters:
    `args` - contains options for the instance query

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