org.apache.metamodel.query

Class Query

java.lang.Object

org.apache.metamodel.util.BaseObject

org.apache.metamodel.query.Query

All Implemented Interfaces:

Serializable, Cloneable

public final class Query
extends BaseObject
implements Cloneable, Serializable

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 Also:

DataContext, Serialized Form

Constructor Summary

Constructors

Constructor and Description
Query()

Method Summary

Modifier and Type	Method and Description
Query	clone()
protected void	decorateIdentity(List<Object> identifiers) Subclasses should implement this method and add all fields to the list that are to be included in equals(...) and hashCode() evaluation
Query	from(FromItem... items)
Query	from(String expression)
Query	from(Table table)
Query	from(Table table, String alias)
Query	from(Table leftTable, Table rightTable, JoinType joinType, Column leftOnColumn, Column rightOnColumn)
Integer	getFirstRow() Gets the first row (aka offset) of the query's result, or null if none is specified.
FromClause	getFromClause()
GroupByClause	getGroupByClause()
FilterClause	getHavingClause()
Integer	getMaxRows()
OrderByClause	getOrderByClause()
SelectClause	getSelectClause()
FilterClause	getWhereClause()
Query	groupBy(Column... columns)
Query	groupBy(GroupByItem... items)
Query	groupBy(List<Column> columns)
Query	groupBy(String... groupByTokens)
Query	having(Column column, OperatorType operatorType, Object operand)
Query	having(FilterItem... items)
Query	having(FunctionType function, Column column, OperatorType operatorType, Object operand)
Query	having(String... havingItemTokens)
InvokableQuery	invokable(DataContext dataContext)
Query	orderBy(Column column)
Query	orderBy(Column column, OrderByItem.Direction direction)
Query	orderBy(OrderByItem... items)
Query	orderBy(String... orderByTokens)
Query	select(Column... columns)
Query	select(Column column, FromItem fromItem)
Query	select(FunctionType functionType, Column column)
Query	select(List<Column> columns)
Query	select(SelectItem... items)
Query	select(String expression) Adds a selection to this query.
Query	select(String expression, boolean allowExpressionBasedSelectItem) Adds a selection to this query.
Query	select(String expression, String alias)
Query	selectAll() Select all available select items from all currently available FROM items.
Query	selectAll(FromItem fromItem)
Query	selectCount()
Query	selectDistinct()
Query	setFirstRow(Integer firstRow) Sets the first row (aka offset) of the query's result.
Query	setMaxRows(Integer maxRows) Sets the maximum number of rows to be queried.
String	toSql()
protected String	toSql(boolean includeSchemaInColumnPaths)
String	toString()
Query	where(Column column, OperatorType operatorType, Object operand)
Query	where(FilterItem... items)
Query	where(Iterable<FilterItem> items)
Query	where(SelectItem selectItem, OperatorType operatorType, Object operand)
Query	where(String... whereItemTokens)

Methods inherited from class org.apache.metamodel.util.BaseObject

classEquals, equals, hashCode

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Query

public Query()

Method Detail

select

public Query select(Column column,
                    FromItem fromItem)

select

public Query select(List<Column> columns)

select

public Query select(Column... columns)

select

public Query select(SelectItem... items)

select

public Query select(FunctionType functionType,
                    Column column)

select

public Query select(String expression,
                    String alias)

select

public Query select(String expression)

Adds a selection to this query.

Parameters:

expression -

Returns:

select

public Query select(String expression,
                    boolean allowExpressionBasedSelectItem)

Adds a selection to this query.

Parameters:

expression - a textual representation of the select item, e.g. "MAX(foo)" or just "foo", where "foo" is a column name.

allowExpressionBasedSelectItem - whether or not expression-based select items are allowed or not (see SelectItem.getExpression().

Returns:

selectAll

public Query selectAll()

Select all available select items from all currently available FROM items. Equivalent of the expression "SELECT * FROM ..." in SQL.

Returns:

selectAll

public Query selectAll(FromItem fromItem)

selectDistinct

public Query selectDistinct()

selectCount

public Query selectCount()

from

public Query from(FromItem... items)

from

public Query from(Table table)

from

public Query from(String expression)

from

public Query from(Table table,
                  String alias)

from

public Query from(Table leftTable,
                  Table rightTable,
                  JoinType joinType,
                  Column leftOnColumn,
                  Column rightOnColumn)

groupBy

public Query groupBy(String... groupByTokens)

groupBy

public Query groupBy(GroupByItem... items)

groupBy

public Query groupBy(Column... columns)

groupBy

public Query groupBy(List<Column> columns)

orderBy

public Query orderBy(OrderByItem... items)

orderBy

public Query orderBy(String... orderByTokens)

orderBy

public Query orderBy(Column column)

orderBy

public Query orderBy(Column column,
                     OrderByItem.Direction direction)

where

public Query where(FilterItem... items)

where

public Query where(Iterable<FilterItem> items)

where

public Query where(String... whereItemTokens)

where

public Query where(SelectItem selectItem,
                   OperatorType operatorType,
                   Object operand)

where

public Query where(Column column,
                   OperatorType operatorType,
                   Object operand)

having

public Query having(FilterItem... items)

having

public Query having(FunctionType function,
                    Column column,
                    OperatorType operatorType,
                    Object operand)

having

public Query having(Column column,
                    OperatorType operatorType,
                    Object operand)

having

public Query having(String... havingItemTokens)

toString

public String toString()

Overrides:

toString in class BaseObject

toSql

public String toSql()

toSql

protected String toSql(boolean includeSchemaInColumnPaths)

getSelectClause

public SelectClause getSelectClause()

getFromClause

public FromClause getFromClause()

getWhereClause

public FilterClause getWhereClause()

getGroupByClause

public GroupByClause getGroupByClause()

getHavingClause

public FilterClause getHavingClause()

getOrderByClause

public OrderByClause getOrderByClause()

setMaxRows

public Query setMaxRows(Integer maxRows)

Sets the maximum number of rows to be queried. If the result of the query yields more rows they should be discarded.

Parameters:

maxRows - the number of desired maximum rows. Can be null (default) for no limits

Returns:

this query

getMaxRows

public Integer getMaxRows()

Returns:

the number of maximum rows to yield from executing this query or null if no maximum/limit is set.

setFirstRow

public Query setFirstRow(Integer firstRow)

Sets the first row (aka offset) of the query's result. The row number is 1-based, so setting a first row value of 1 is equivalent to not setting it at all..

Parameters:

firstRow - the first row, where 1 is the first row.

Returns:

this query

getFirstRow

public Integer getFirstRow()

Gets the first row (aka offset) of the query's result, or null if none is specified. The row number is 1-based, so setting a first row value of 1 is equivalent to not setting it at all..

Returns:

the first row (aka offset) of the query's result, or null if no offset is specified.

invokable

public InvokableQuery invokable(DataContext dataContext)

decorateIdentity

protected void decorateIdentity(List<Object> identifiers)

Description copied from class: BaseObject

Subclasses should implement this method and add all fields to the list that are to be included in equals(...) and hashCode() evaluation

Specified by:

decorateIdentity in class BaseObject

clone

public Query clone()

Overrides:

clone in class Object