Examples of org.apache.metamodel.query.Query

org.apache.metamodel.query.Query
Represents a query to retrieve data by. A query is made up of six clauses, equivalent to the SQL standard:
- the SELECT clause, which define the wanted columns of the resulting DataSet
- the FROM clause, which define where to retrieve the data from
- the WHERE clause, which define filters on the retrieved data
- the GROUP BY clause, which define if the result should be grouped and aggregated according to some columns acting as categories
- the HAVING clause, which define filters on the grouped data
- the ORDER BY clause, which define sorting of the resulting dataset
In addition two properties are applied to queries to limit the resulting dataset:
- First row: The first row (aka. offset) of the result of the query.
- Max rows: The maximum amount of rows to return when executing the query.
Queries are executed using the DataContext.executeQuery method or can alternatively be used directly in JDBC by using the toString() method. @see DataContext

        assertEquals(XlsxSpreadsheetReaderDelegate.class, dc.getSpreadsheetReaderDelegateClass());


        Table table = dc.getDefaultSchema().getTableByName("sh1");
        assertEquals("[Foo, Bar]", Arrays.toString(table.getColumnNames()));


        Query q = dc.query().from(table).select("Foo").toQuery();
        DataSet ds = dc.executeQuery(q);


        assertTrue(ds.next());
        assertEquals("1", ds.getRow().getValue(0).toString());
        assertEquals("", ds.getRow().getStyle(0).toString());

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        Table table = schema.getTable(0);
        Column column = table.getColumn(0);


        // query another DataContext using the schemas of the one above
        ExcelDataContext dc2 = new ExcelDataContext(new File("src/test/resources/Spreadsheet2007.xlsx"));
        DataSet ds = dc2.executeQuery(new Query().from(table).select(column));


        // previously we would crash at this point!


        assertNotNull(ds);
        ds.close();

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        return _delegate.parseQuery(queryString);
    }


    @Override
    public DataSet executeQuery(String queryString) throws MetaModelException {
        final Query query = parseQuery(queryString);
        final DataSet dataSet = executeQuery(query);
        return dataSet;
    }

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  protected DataSet materializeMainSchemaTable(Table table, Column[] columns,
      int maxRows) {
    // find the appropriate datacontext to execute a simple
    // table materialization query
    DataContext dc = _dataContextRetrievalFunction.eval(table);
    Query q = new Query().select(columns).from(table);
    if (maxRows >= 0) {
      q.setMaxRows(maxRows);
    }
    return dc.executeQuery(q);
  }

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    @Override
    public DataSet executeQuery(CompiledQuery compiledQuery, Object... values) {


        final JdbcCompiledQuery jdbcCompiledQuery = (JdbcCompiledQuery) compiledQuery;


        final Query query = jdbcCompiledQuery.getQuery();
        final int countMatches = jdbcCompiledQuery.getParameters().size();


        final int valueArrayLength = values.length;


        if (countMatches != valueArrayLength) {

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    public void testApproximatedCountSmallFile() throws Exception {
        DataContext dc = new CsvDataContext(new File("src/test/resources/csv_people.csv"));


        Table table = dc.getDefaultSchema().getTables()[0];
        Query q = dc.query().from(table).selectCount().toQuery();
        SelectItem selectItem = q.getSelectClause().getItem(0);
        selectItem.setFunctionApproximationAllowed(true);


        DataSet ds = dc.executeQuery(q);
        assertTrue(ds.next());
        Object[] values = ds.getRow().getValues();

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    public void testFilterOnNumberColumn() throws Exception {
        CsvDataContext dc = new CsvDataContext(new File("src/test/resources/csv_people.csv"));
        Table table = dc.getDefaultSchema().getTables()[0];


        Query q = dc.query().from(table).select("name").where("age").greaterThan(18).toQuery();
        List<Object[]> result = dc.executeQuery(q).toObjectArrays();
        assertEquals(2, result.size());
        assertEquals("[michael]", Arrays.toString(result.get(0)));
        assertEquals("[hillary]", Arrays.toString(result.get(1)));
    }

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        doTicketFileTests(dc);
    }


    public void doTicketFileTests(DataContext dc) {
        Table table = dc.getDefaultSchema().getTables()[0];
        Query q = dc.query().from(table).select(table.getColumns()).toQuery();


        DataSet dataSet = dc.executeQuery(q);
        List<Object[]> objectArrays = dataSet.toObjectArrays();
        assertEquals(13, objectArrays.get(0).length);
        assertEquals(36, objectArrays.size());

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        assertEquals("2", columns[0].getName());
        assertEquals("michael", columns[1].getName());
        assertEquals("male", columns[2].getName());
        assertEquals("19", columns[3].getName());


        Query query = dc.query().from(table).select(table.getColumnByName("michael")).toQuery();


        DataSet dataSet = dc.executeQuery(query);
        assertTrue(dataSet.next());
        assertEquals("peter", dataSet.getRow().getValue(0));
        assertTrue(dataSet.next());

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        assertEquals("A", columns[0].getName());
        assertEquals("B", columns[1].getName());
        assertEquals("C", columns[2].getName());
        assertEquals("D", columns[3].getName());


        Query query = dc.query().from(table).select(table.getColumnByName("B")).toQuery();


        DataSet dataSet = dc.executeQuery(query);
        assertTrue(dataSet.next());
        assertEquals("name", dataSet.getRow().getValue(0));
        assertTrue(dataSet.next());

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org.apache.metamodel.AbstractDataContext

org.apache.metamodel.CompositeDataContextTest

org.apache.metamodel.CompositeQueryDelegate

org.apache.metamodel.convert.ConvertedDataSetInterceptorTest

org.apache.metamodel.convert.Converters

org.apache.metamodel.convert.ConvertersTest

org.apache.metamodel.csv.CsvBigFileMemoryTest

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org.apache.metamodel.DB2Test

org.apache.metamodel.dbmains.PostgresqlMain

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