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In raw SQL, you can easily include columns from more than one table in a
SELECT query.
With EOF, you ordinarily don't want to do that, you ordinarily are
fetching a particular entity, and you want only the columns of the table
corresponding to that entity. One way to get other table's columns in
your entity is with flattened attributes, of course.
But with raw rows, you don't need to add any flattened attributes to your
model. You can include a 'raw row key path' that traverses relationships,
for instance 'department.name' if the primary entity of your fetch is
Employee. And exactly the right thing just happens, great. So EOF can
sometimes do this with a raw row fetch.
My problem is that, for reasons I won't go into here, I need to set up a
fetch using the EOSQLQualifier API. And the only way to specify which
columns should be in the fetch seems to be to pass in an array of
EOAttributes, not a keypath. [See prepareSelectExpressionWithAttributes
and/or assembleSelectStatementWithAttributes---both want an array of
EOAttributes]. And it assumes all those EOAttributes are in the
'primary' entity, if you pass in an EOAttribute from some other entity,
it generates bad SQL. But there must be SOME way to do this----calling
setRawRowKeyPaths() on an EOFetchSpecification, using key paths that
traverse relationships, well, that WORKS, and it must be using
EOSQLExpression to do it's thing...
But I can't figure out how to make EOSQLExpression do that. Anyone
especially wise in the ways of EOSQLExpression and related classes, who
can help me out?
--Jonathan
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