org.apache.metamodel.query

Class FromItem

java.lang.Object

org.apache.metamodel.util.BaseObject

org.apache.metamodel.query.FromItem

All Implemented Interfaces:

Serializable, Cloneable, QueryItem

public class FromItem
extends BaseObject
implements QueryItem, Cloneable

Represents a FROM item. FROM items can take different forms:

• table FROMs (eg. "FROM products p")
• join FROMs with an ON clause (eg. "FROM products p INNER JOIN orders o ON p.id = o.product_id")
• subquery FROMs (eg. "FROM (SELECT * FROM products) p")
• expression FROM (any string based from item)

See Also:

FromClause, Serialized Form

Constructor Summary

Constructors

Constructor and Description
FromItem(JoinType join, FromItem leftSide, FromItem rightSide, SelectItem[] leftOn, SelectItem[] rightOn) Constructor for advanced join types with custom relationships
FromItem(JoinType join, Relationship relationship) Constructor for join FROM clauses that join two tables using their relationship.
FromItem(Query subQuery) Constructor for sub-query FROM clauses
FromItem(String expression) Creates a single unvalidated from item based on a expression.
FromItem(Table table) Constructor for table FROM clauses

Method Summary

Modifier and Type	Method and Description
protected FromItem	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
String	getAlias()
String	getAlias(Table table) Gets the alias of a table, if it is registered (and visible, ie.
String	getExpression()
JoinType	getJoin()
SelectItem[]	getLeftOn()
FromItem	getLeftSide()
Query	getQuery()
SelectItem[]	getRightOn()
FromItem	getRightSide()
String	getSameQueryAlias()
Query	getSubQuery()
Table	getTable()
FromItem	setAlias(String alias)
QueryItem	setQuery(Query query)
String	toSql()
String	toSql(boolean includeSchemaInColumnPaths)
String	toString()
String	toStringNoAlias()
String	toStringNoAlias(boolean includeSchemaInColumnPaths)

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

FromItem

public FromItem(Table table)

Constructor for table FROM clauses

FromItem

public FromItem(Query subQuery)

Constructor for sub-query FROM clauses

Parameters:

subQuery - the subquery to use

FromItem

public FromItem(JoinType join,
                Relationship relationship)

Constructor for join FROM clauses that join two tables using their relationship. The primary table of the relationship will be the left side of the join and the foreign table of the relationship will be the right side of the join.

Parameters:

join - the join type to use

relationship - the relationship to use for joining the tables

FromItem

public FromItem(JoinType join,
                FromItem leftSide,
                FromItem rightSide,
                SelectItem[] leftOn,
                SelectItem[] rightOn)

Constructor for advanced join types with custom relationships

Parameters:

join - the join type to use

leftSide - the left side of the join

rightSide - the right side of the join

leftOn - what left-side select items to use for the ON clause

rightOn - what right-side select items to use for the ON clause

FromItem

public FromItem(String expression)

Creates a single unvalidated from item based on a expression. Expression based from items are typically NOT datastore-neutral but are available for special "hacking" needs. Expression based from items can only be used for JDBC based datastores since they are translated directly into SQL.

Parameters:

expression - An expression to use for the from item, for example "MYTABLE".

Method Detail

getAlias

public String getAlias()

getSameQueryAlias

public String getSameQueryAlias()

setAlias

public FromItem setAlias(String alias)

getTable

public Table getTable()

getSubQuery

public Query getSubQuery()

getJoin

public JoinType getJoin()

getLeftSide

public FromItem getLeftSide()

getRightSide

public FromItem getRightSide()

getLeftOn

public SelectItem[] getLeftOn()

getRightOn

public SelectItem[] getRightOn()

getExpression

public String getExpression()

toSql

public String toSql()

Specified by:

toSql in interface QueryItem

toSql

public String toSql(boolean includeSchemaInColumnPaths)

Specified by:

toSql in interface QueryItem

toStringNoAlias

public String toStringNoAlias()

toStringNoAlias

public String toStringNoAlias(boolean includeSchemaInColumnPaths)

getAlias

public String getAlias(Table table)

Gets the alias of a table, if it is registered (and visible, ie. not part of a sub-query) in the FromItem

Parameters:

table - the table to get the alias for

Returns:

the alias or null if none is found

getQuery

public Query getQuery()

Specified by:

getQuery in interface QueryItem

setQuery

public QueryItem setQuery(Query query)

Specified by:

setQuery in interface QueryItem

clone

protected FromItem clone()

Overrides:

clone in class Object

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

toString

public String toString()

Specified by:

toString in interface QueryItem

Overrides:

toString in class BaseObject