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

    }


    private Integer getSubQueryFromItemIndex() {
        List<FromItem> fromItems = _query.getFromClause().getItems();
        for (int i = 0; i < fromItems.size(); i++) {
            Query subQuery = fromItems.get(i).getSubQuery();
            if (subQuery != null) {
                if (isSplittable(subQuery)) {
                    return i;
                }
            }

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    private long getRowCount(Query q) {
        q = q.clone();
        SelectItem countAllItem = SelectItem.getCountAllItem();
        if (q.getGroupByClause().getItemCount() > 0) {
            q = new Query().from(new FromItem(q).setAlias("sq")).select(countAllItem);
        } else {
            q.getSelectClause().removeItems();
            q.select(countAllItem);
        }
        Row row = MetaModelHelper.executeSingleRowQuery(_dataContext, q);

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        assertEquals("[greeting, greeter]", Arrays.toString(table.getColumnNames()));
        assertEquals(10, table.getColumnByName("greeting").getColumnSize().intValue());
        assertEquals(10, table.getColumnByName("greeter").getColumnSize().intValue());


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


        assertTrue(ds.next());
        assertEquals("[hello, world]", Arrays.toString(ds.getRow().getValues()));
        assertTrue(ds.next());

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        Table table = schema.getTableByName("example_simple1.txt");
        assertEquals("Table[name=example_simple1.txt,type=TABLE,remarks=null]", table.toString());


        assertEquals("[A, B]", Arrays.toString(table.getColumnNames()));


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


        assertTrue(ds.next());
        assertEquals("greeting", ds.getRow().getValue(0));
        assertEquals("greeter", ds.getRow().getValue(1));

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        assertEquals(1, table.getColumnByName("i").getColumnSize().intValue());
        assertEquals(8, table.getColumnByName("greeting").getColumnSize().intValue());
        assertEquals(7, table.getColumnByName("greeter").getColumnSize().intValue());


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


        assertTrue(ds.next());
        assertEquals("[1, hello, world]", Arrays.toString(ds.getRow().getValues()));
        assertTrue(ds.next());

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                        7 }, false));


        Table table = dc.getDefaultSchema().getTables()[0];
        assertEquals("[i, greet, inggree]", Arrays.toString(table.getColumnNames()));


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


        assertTrue(ds.next());
        assertEquals("[1, hello, worl]", Arrays.toString(ds.getRow().getValues()));
        assertTrue(ds.next());

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                        9 }, false));


        Table table = dc.getDefaultSchema().getTables()[0];
        assertEquals("[i, greeting, greeter]", Arrays.toString(table.getColumnNames()));


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


        assertTrue(ds.next());
        assertEquals("[1, hello, world]", Arrays.toString(ds.getRow().getValues()));
        assertTrue(ds.next());

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        q = MetaModelHelper.parseQuery(dc, "SELECT a.foo AS foobarbaz FROM sch.tbl a WHERE foobarbaz = '123'");
        assertEquals("SELECT a.foo AS foobarbaz FROM sch.tbl a WHERE foobarbaz = '123'", q.toSql());
    }


    public void testSelectDistinct() throws Exception {
        Query q = MetaModelHelper.parseQuery(dc, "SELECT DISTINCT foo, bar AS f FROM sch.tbl");
        assertEquals("SELECT DISTINCT tbl.foo, tbl.bar AS f FROM sch.tbl", q.toSql());
    }

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        Query q = MetaModelHelper.parseQuery(dc, "SELECT DISTINCT foo, bar AS f FROM sch.tbl");
        assertEquals("SELECT DISTINCT tbl.foo, tbl.bar AS f FROM sch.tbl", q.toSql());
    }


    public void testSimpleSelectFrom() throws Exception {
        Query q = MetaModelHelper.parseQuery(dc, "SELECT foo\nFROM sch.tbl");
        assertEquals("SELECT tbl.foo FROM sch.tbl", q.toSql());


        assertEquals(1, q.getFromClause().getItemCount());
        FromItem fromItem = q.getFromClause().getItem(0);
        assertNull("FROM item was an expression based item, which indicates it was not parsed",
                fromItem.getExpression());
        assertNotNull(fromItem.getTable());
        assertEquals("tbl", fromItem.getTable().getName());


        assertEquals(1, q.getSelectClause().getItemCount());
        SelectItem selectItem = q.getSelectClause().getItem(0);
        assertNull("SELECT item was an expression based item, which indicates it was not parsed",
                selectItem.getExpression());
        assertNotNull(selectItem.getColumn());
        assertEquals("foo", selectItem.getColumn().getName());


        assertNull(q.getFirstRow());
        assertNull(q.getMaxRows());
    }

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        assertNull(q.getFirstRow());
        assertNull(q.getMaxRows());
    }


    public void testCarthesianProduct() throws Exception {
        Query q = MetaModelHelper.parseQuery(dc,
                "  SELECT a.foo,b.bar FROM      sch.tbl a, sch.tbl b \t WHERE a.foo = b.foo");
        assertEquals("SELECT a.foo, b.bar FROM sch.tbl a, sch.tbl b WHERE a.foo = b.foo", q.toSql());


        List<FromItem> fromItems = q.getFromClause().getItems();
        assertNotNull(fromItems.get(0).getTable());
        assertNotNull(fromItems.get(1).getTable());


        List<FilterItem> whereItems = q.getWhereClause().getItems();
        assertNotNull(whereItems.get(0).getSelectItem().getColumn());
        assertNotNull(whereItems.get(0).getSelectItem().getFromItem().getTable());
    }

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