[TORQUE-290] Improve building from clause in subselect

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0
• Fix Version/s: 5.0
• Component/s: Runtime
• Labels: incompatibleChange
• Assignee: Thomas Fox
• Reporter: Thomas Fox
• Created: 28/Jun/13 11:39
• Updated: 06/Oct/15 03:17
• Resolved: 06/Oct/15 03:17

Description

Currently, it is not easily possible to reference columns in the main select from a subselect.
For example, to select authors which have published exactly one book, one can use the SQL:
SELECT * FROM author WHERE (SELECT COUNT FROM book WHERE book.author_id=author.author_id)=1

One would like to achieve this by

Criteria subselect = new Criteria();
subselect.where(BookPeer.AUTHOR_ID, AuthorPeer.AUTHOR_ID);
subselect.addSelectColumn(new Count("*"));

Criteria criteria = new Criteria();
criteria.where(subselect, 1);

List<Author> result = AuthorPeer.doSelect(criteria);

but the SQL results in (note the additional author in the from clause of the subselect)
SELECT * FROM author WHERE (SELECT COUNT FROM book, author WHERE book.author_id=author.author_id)=1

So the desired behavior is:
If a table also exists in the from clause of the outer criteria, it should not be added to the from clause of the subselect

NOTE1: This change can change the behaviour of Torque in existing code
NOTE2: Workarounds exist, e.g. defining the FROM clause of the subselect manually using Criteria.addFrom() or using "new ColumnImpl(null,null,null,AuthorPeer.AUTHOR_ID.getSqlExpression())" as join column in the WHERE clause of the subselect.

Sub-Tasks

• Make PreparedStatementPart an interface: Resolved